Solution-Focused Therapy
Introduction
Treyentered the office cautiously and took a seat across the table from me.1 He glanced around the room at the bookshelves, wall hangings, and a few other items—anything but me. Trey, a 9-year-old African American student in an inner-city elementary school, was referred by his teachers for a psychoeducational evaluation due to academic problems. As the school psychologist, I was required to complete a social history interview and form at the start of every evaluation, which typically took about 5 minutes. As it turns out, my conversation with Trey that day was anything but typical.
After a few introductory comments, I asked who he lived with at home. “My aunt and five cousins,” Trey replied. His school file stated that he had been removed from his mother’s custody the previous year due to child abuse and that his father died when Trey was 6. When I told him I was sorry about his father’s passing, he quietly told me his father
1 In all clinical case material in this book identities have been disguised and other steps have been taken to protect client confidentiality.
https://doi.org/10.1037/0000370-001
Solution-Focused Therapy, by J. J. Murphy
Copyright © 2024 by the American Psychological Association. All rights reserved.
was murdered by “a guy named George” in the kitchen of their apartment. “They were yelling, and George shot him. The police came and took George away, and they took me to my aunt’s house.” The social history interview had taken an unexpected turn.
“I bet it’s hard not seeing your dad,” I said. Trey nodded and described other struggles involving various family members. He had two older brothers named James and Robert. James was in prison and Robert was on probation. Trey had been in three different schools during the past 3 years. After telling me his aunt might move again, he put his face in his hands and sobbed.
We sat in silence for a minute or so before I noticed a few tears collecting on the table under Trey’s face. I was at a loss for words. We sat for another minute, Trey with his face in his hands and me staring a hole in the table. I couldn’t shake the idea that Trey had suffered more in 9 years than some people do in a lifetime.
I finally broke the silence. “With everything you’ve been through, how do you keep hanging in there and coming to school?”
Trey looked at me for the first time and said, “My aunt always tells me to never give up because quitters don’t make it.”
I followed his lead by asking, “What else does she say or do that helps you?”
Trey replied, “She’s always saying, ‘try hard,’ ‘do your best,’ and stuff like that. And that I’d be the first one in the family to graduate from high school.”
When asked what else kept him going, Trey described several coping skills and other resources. I felt myself becoming more hopeful, and Trey seemed more energized as the conversation shifted from what was wrong or lacking in his life to what was right and working. He spoke faster and with more expression. He leaned forward, held his head higher, and made more eye contact. Among other things, I learned that his brother Robert occasionally helped him with homework and that he did better in math when teachers gave him more time to complete class work. I thanked him for talking with me and walked him back to class.
Trey and I completed the evaluation a few weeks later, and my report included the following recommendations taken directly from our previous
conversation: additional homework help from Robert, extra time for math work in class, tutoring from older students at school, and continued encouragement from his aunt. Although I did not think of it in these terms at the time, every suggestion was built on what was already available and working in Trey’s life—his ideas, social supports, and other indigenous strengths and resources in his life.
I began to search for a more systematic way to initiate collaborative, client-directed, strengths-based conversations like the first one with Trey. The search led to a small group of clinicians in Milwaukee, led by Steve de Shazer and Insoo Kim Berg, who were experimenting with an innovative brief therapy approach. They called it “solution-focused” brief therapy to highlight the emphasis on what clients wanted from therapy and what they were already doing or already had in their lives that would help toward achieving it. This book uses the shorter term solution-focused therapy (SFT) to capture the approach’s essence and distinguish it from problemfocused approaches that have dominated the psychotherapy profession for over a century.
WHAT IS SOLUTION-FOCUSED THERAPY ?
SFT is a collaborative approach that invites clients2 to describe what they want from therapy and apply what they already have in place toward achieving it in the shortest time possible. Therapists are guided by three self-talk questions:
◾ What does the client want from therapy?
◾ What does the client already have toward achieving it?
◾ What progress has the client already made and what are some possible next signs or next steps toward further progress?
2 In this book, the term clients refers to individuals, couples, families, or other therapy participants. Therapists and practitioners include psychotherapists, psychiatrists, counselors, social workers, and other service providers. Therapist is used in client illustrations and dialogues for the sake of consistency. Solutions refers to positive steps toward desired outcomes rather than ideal outcomes or absence of problems.
These questions translate into the following three main tasks of SFT:
1. Setting a direction on the basis of what the client wants from therapy: What are your best hopes from talking with me? How would your life be different if you achieved those hopes?
2. Building on exceptions and other resources that are already happening and available in the client’s life: When is/was the problem less noticeable? Tell me about a time your best hopes have happened. How did you make that happen? What/who else might help you move closer to your best hopes?
3. E xploring progress toward desired outcomes: What’s better since we last met? How did you move up on the 0–10 scale? What might be the next small sign/step toward further progress?
These tasks represent the entirety of SFT and occur in varying degrees and sequences during most sessions. The three main techniques of SFT are asking, listening, and amplifying. Therapists ask useful questions, listen closely to clients’ responses, and amplify aspects of their responses and lives that support desired outcomes. When being purely solution-focused, there is rarely anything else the therapist does outside of these activities. The definition of SFT highlights several key features. SFT is:
Collaborative
SFT is a collaborative, client-directed approach that invites clients to participate in every aspect of therapy to the extent they are willing and able to do so. In contrast to approaches in which therapists prescribe interventions based on their expertise and theoretical perspective, solutionfocused therapists elicit solutions from clients by approaching them from a position of humility and “not knowing” (H. Anderson, 2007).
Assuming a stance of not knowing does not mean relinquishing one’s expertise or influence. As Weakland (1993) noted, “Influence is inherent in all human interaction. . . . The only choice is between doing so without reflection, or even with attempted denial, and doing so deliberately and responsibly” (p. 143). Microanalysis research indicates that therapists of
all orientations influence the content of conversation by deciding what to ask and not ask, what to follow up on and let go, and so forth (Bavelas et al., 2014). In SFT, these decisions are guided by the client’s goals and responses rather than the therapist’s preferences. As Iveson et al. (2012) said, the therapist “would rather be invisible than significant; someone who generates and manages a conversation in which the client hears his or her own words either for the first time or with fresh ears” (p. 127).
Invitational
When SFT practitioners ask questions or offer suggestions, they are presented as invitations rather than directives. For a client who reported recent improvements, the therapist might offer the following suggestion: “It may be helpful to watch for small signs of progress. How does that sound to you?” The invitational tone is conveyed by the phrase, “It may be helpful” and the question, “How does that sound to you?” Presenting questions and suggestions in this manner encourages clients to freely accept, reject, or modify them as needed with no pressure or pushback from the therapist.
Descriptive
Solution-focused therapists elicit descriptions of client hopes, resources, and progress rather than interpreting client actions, motives, and feelings. Consider the following detail-gathering sequence of questions: “What will you notice first when things get a little better? Then what? Who else will notice? How might they respond? What will that be like for you?” Although this sequence of questions lacks the most important element of the conversation—the client’s response—it briefly illustrates SFT’s emphasis on description.
Focused on What Clients Want
Focusing on what clients want more of (vs. less of) is why SFT is considered an addition (vs. subtraction) approach. The entire SFT process
revolves around what the client wants from therapy, which is addressed at the very outset of services (“What are your best hopes from this? What will be different to tell you it was useful?”). Asking what clients want from therapy neither denies the problem nor prohibits clients from discussing problems—it simply invites them to focus on what they want instead . This phase of SFT is referred to as formulating goals or setting a direction. 3 Regardless of one’s terminology, the first and most important task of SFT is to determine what the client wants from it.
Focused on What Clients Have
Instead of assuming that client problems indicate personal deficiencies, solution-focused therapists assume clients possess the resources needed to improve their lives. This does not imply that clients would not benefit from additional knowledge and skills. It just means that SFT focuses on helping them build solutions from what is already available and working in their lives—strengths, attributes, successes, social supports, and other resources that can help them achieve hoped-for outcomes.
Brief (Shortest Time Possible)
SFT is brief by design versus default, and every session is approached as if it were the last. This practical mindset expedites change by keeping therapists and clients on track. It also explains why SFT techniques are commonly used in single-session therapy (Hoyt et al., 2018). The “brief” component of SFT does not mean clients are rushed into action or therapists are insensitive to their struggles. Brevity is more of a by-product than a goal of SFT. Therapists rarely set a preestablished limit on the length of therapy
3 I prefer the terms desired (or hoped-for) outcome, preferred future, and setting a direction to the more conventional language of “goals and goal setting” because they effectively portray the SFT process of helping clients describe what they want from therapy and scale their movement and progress toward achieving it. If you prefer goal-based language or are required to use it for documentation purposes, then you can view the client’s desired outcome as a general goal, the preferred future as a detailed goal, and setting a direction as goal setting.
because that decision, like others, is made in close collaboration with clients. Agencies and therapists that have used SFT for many years have estimated the average length of therapy to be 3 to 6.5 sessions (Macdonald, 2017). Perhaps the most practical guideline for determining the length of therapy was offered by de Shazer, who said “as long as it takes and not one session more” (as cited in Ratner et al., 2012).
Although most therapists do not think of themselves as brief therapists, research suggests they are doing “unplanned brief therapy” (10 sessions or fewer) regardless of their preferences, theoretical orientation, or training (Levenson, 2017). It appears that clients will either achieve their therapeutic goals during that time or drop out if they don’t (Muran et al., 2009; Wierzbicki & Pekarik, 1993). These findings suggest that therapists do not have much of a choice as to whether or not to do brief therapy. The choice is whether to do so by design or default. The fact that SFT has always been brief by design—in combination with its evidence base and multic ultural orientation—helps to explain its increased popularity among therapists and clients throughout the world (Neipp & Beyebach, 2022). Since most clients prefer as few sessions as possible, it seems respectful to honor that preference regardless of one’s therapy approach.
SFT AND EVIDENCE-BASED PRACTICE
In 2005, the American Psychological Association (APA) established the Task Force on Evidence-Based Practice to define evidence-based practice in psychotherapy and other psychological services. The task force was made up of scientists and practitioners from diverse theoretical perspectives. Their work resulted in a tripartite definition of evidence-based practice as “the integration of the best available research with clinical expertise in the context of patient characteristics, culture, and preferences” (APA Task Force on Evidence-Based Practice, 2006, p. 273). Since this is part of an APA book series, it seems fitting to address the compatibility between SFT and the three main features of evidence-based practice— research-informed practice; clinical expertise; and client characteristics, culture, and preferences.
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(above), boundary between pairing animals; (below), first fission; single vertical line, continuity or enlargement. M, Meganucleus; µ, micronucleus; Z, zygote-nucleus
F . 54. Four individuals of Coleps hirtus (Gymnostomaceae) swarming about and ingesting a Vorticella (?) (From Verworn )
The meganucleus lengthens, becomes irregularly constricted, and breaks up into fragments, which are ultimately extruded or partially digested. The micronucleus enlarges (Fig. 52, A) and undergoes three successive divisions, or, strictly speaking, two fissions producing four nuclei, of which one only undergoes the third. The other three nuclei of the second fission degenerate like the meganucleus.[167] Of the two micronuclei of this last division one remains where it is as a "stationary" pairing nucleus, while its sister passes as a "migratory" pairing-nucleus into the other mate, and fuses with its stationary pairing-nucleus. Thus in either mate is formed a "zygote-nucleus," or "fusion-nucleus." All these processes are simultaneous in the two mates; and the migratory nuclei cross one another on the bridge of junction of the two mates (Fig. 52, C). Each mate now has its original cytoplasm (subject to the qualification above), but its old nuclear apparatus is replaced by the fusionnucleus. This new nucleus undergoes repeated fissions; its offspring enlarge unequally, the larger being differentiated as mega-, the smaller as micro-nuclei. The mates now separate (Fig. 52, F, G), and
by the first (or subsequent) fission of each, the new mega- and micro-nuclei are distributed to the offspring. Colpidium colpoda offers the simplest case, on which we have founded our diagram showing the nuclear relations. During conjugation the oral apparatus often atrophies, and is regenerated; and in some cases the pellicle and ciliary apparatus are also "made over."
F . 55.—Paramecium caudatum (Aspirotrichaceae). A, The living animal from the ventral aspect; B, the same in optical section, the arrows show the course taken by food-particles. buc.gr, Buccal groove; cort, cortex; cu, cuticle; c.vac, contractile vacuole; f.vac, food vacuole; gul, gullet; med, medulla; mth, mouth; nu, meganucleus; pa.nu, micronucleus; trch, trichocysts discharged. (From Parker's Biology.)
In the Peritrichaceae the mates are unequal; the larger is the normal cell, and is fixed; the smaller, mobile, is derived from an ordinary individual by brood-divisions, which only occur under the conditions that induce conjugation (Fig. 60). Here, though the two pairs of nuclei are formed, it is only the migratory nuclei that unite, the stationary ones aborting in both mates. During the final processes of conjugation the smaller mate is absorbed into the body of the larger, and so plays the part of male there. But this process, though one of true binary sex, is clearly derived from the peculiar type of equal reciprocal conjugation of the other Infusoria.
The Ciliata are almost all free-swimming animals with the exception of most of the Peritrichaceae, and of the genera we now cite. Folliculina forms a sessile tube open at either end; and Schizotricha socialis inhabits the open mouths of a branching gelatinous tubular stem, obviously secreted by the hinder end of the animal, and forking at each fission to receive the produce. A similar habit to the latter characterises Maryna socialis; all three species are marine, and were described by Gruber.[168] Stentor habitually attaches itself by processes recalling pseudopodia, and often forms a gelatinous sheath.
The majority of the Oligotrichaceous Tintinnidae inhabit free chitinous tests often beautifully fenestrated, as in Dictyocystis.
Many genera are parasitic in the alimentary canal of various Metazoa, but none appear to be seriously harmful except Ichthyophtheirius, which causes an epidemic in fresh-water fish. Quite a peculiar fauna inhabit the paunch of Ruminants. Nyctotherus and Balantidium are occasionally found in the alimentary canal of Man.[169]
The Gymnostomaceae are predaceous, feeding for the most part on smaller Ciliates. We have described the peculiar character of the mouth and pharynx in this group, and the mail-like pellicle of Coleps (Fig. 54). Loxophyllum is remarkable for the absence of cilia from one of the sides of its flattened body, and the tufts of trichocysts studding its dorsal edge at regular intervals. Actinobolus has numerous tentacles, exsertile and retractile, each bearing a terminal tuft of trichocysts, which serve to paralyse such active prey as Halteria. Ileonema has one tentacle overhanging the mouth; and Mesodinium has four short sucker-like projections around it.[170] It has only two girdles of cilia, which are stout and resemble finepointed cirrhi. In Dysteria the cilia are exclusively ventral, and the naked dorsal surface has its pellicle condensed into a bivalve shell; a
posterior motile process ("foot") and a complex pharyngeal armature add to the exceptional characters of the genus.
The Aspirotrichaceae are well known to every student of "Elementary Biology" by the "type" Paramecium (Fig. 55), so common in infusions, especially when containing a little animal matter. P. bursaria often contains in its endosarc the green symbiotic Flagellate Zoochlorella Colpoda cucullus, very frequent in vegetable infusions, usually only divides during encystment, and forms a brood of four. Pleuronema chrysalis (Fig. 57) is remarkable for its habit of lying for long periods on its side and for its immense undulating membrane, forming a lip on the left of its mouth; Glaucoma has two, right and left.
F . 56. Trachelius ovum. A, general view; B, section through sucker; C, section through contractile vacuole and its pore of discharge. al, Alveolar layer of ectoplasm; cil, cilia; c v, contractile vacuole; m, mouth; N, meganucleus; s, sucker, from which pass inwards retractile myonemes (After Clara Hamburger )
F . 57. Pleuronema chrysalis (Aspirotrichaceae). A, Unstimulated, lying quiet; B, stimulated, in the act of springing by the stroke of its cilia. (From Verworn )
The Heterotrichaceae present very remarkable forms. Spirostomum is nearly cylindrical, and, a very giant, may attain a length of 4 mm. (1⁄6"). Stentor can attach itself by its hinder end, which is then finely tapered and prolonged into a few pseudopodia; its body is trumpetshaped, with a spiral peristome forming a coil round its wide end, and leading on the left side into the mouth. Many species when attached secrete a gelatinous sheath or tube. S. polymorphus is often coloured green by Zoochlorella (p. 125); S. coeruleus[171] and S. igneus owe their names to the brilliant pigment, blue or scarlet, deposited in granules in lines between the conspicuous longitudinal myonemes. From their large size and elongated meganucleus accompanied by numerous micronuclei, these two genera have frequently been utilised for experiments on regeneration. In Metopus sigmoides the peristomial area forms a dome above its wreath of membranellae; and in M. pyriformis this is so great as to form the larger part of the cell, which is top-shaped, tapering behind to a point. Caenomorpha (Fig. 58) has the same general form, with a peg-like tail, and possesses a girdle of cirrhi.[172] The converse occurs in Bursaria; the cell is a half ellipse, something like a common twin tobacco-pouch when closed: a deep depression thus occupies the whole ventral surface, and opens by a wide slit extending along the anterior end. The peristomial area occupies the dorsal side of the pocket so formed, and the mouth is in the hinder left-hand corner. Blepharisma sp. is parasitic in the Heliozoon Raphidiophrys viridis (Fig. 20, 1, p. 74).
F 58 —Caenomorpha uniserialis crh, Zone of cirrhi; c t, cilia of tail; c v, contractile vacuole; c.w, ciliary wreath; g, granular aggregate; m, zone of membranellae; N, meganucleus; n, micronucleus; oe, pharynx; t, tail-spine; t1 , accessory spine; u.m, undulating membrane; v, vacuole; z, precaudal process. (After Levander.)
Among Oligotrichaceae, Halteria, common among the débris at the bottom of pools in woods containing dead leaves, is remarkable for an equatorial girdle of very long fine setae, and for its rapid erratic darting movements, alternating with a graceful bird-like hover. The Tintinnidae are mostly marine, pelagic, with the general look of a stalkless Vorticella; some have a latticed chitinous shell.[173]
F . 59. Stentor polymorphus. I, Young individual attached, extended; II, adult in fission, contracted; cv in I, afferent canal of contractile vacuole; in II, contractile vacuole; N, moniliform meganucleus (micronuclei omitted); o, mouth; the fine lines are the myoneme fibrils. (From Verworn.)
Among Peritrichaceae, Vorticella (Fig. 60) and its allies have long been known as Bell-animalcules to every student of pond-life. The body has indeed the form of an inverted bell, closed at its mouth by the "peristome," or oral disc; this is a short, inverted truncate cone set obliquely so that its wide base hardly projects at one side, but is tilted high on the other; the edge of the bell is turned out into a rim or "collar," separated from the disc by a deep gutter. The collar, habitually everted, or even turned down, contracts over the retracted disc when the animal is retracted (E2), which is brought about by any sort of shock, or when it swims freely backwards. For the latter purpose a posterior ring of cilia (or rather membranellae) is developed round the hinder end of the bell (A, cr, E3). The cilia of the adoral wreath are very strong, united at the base into a continuous membrane, and indeed themselves partake of the composite nature of membranellae. The wreath forms more than one turn of a righthanded spiral, the innermost turn ending abruptly on the disc, the outer leading down into the mouth at the point where the disc is most tilted and the groove deepest.[174] The pharynx (p) is long, and contains an undulating membrane (u.m) on its inner side projecting out through the mouth, and numerous cilia; it leads deep into the body (p). The first part is distinguished as the "vestibule" (v), as into it opens the anus, and the contractile vacuole (c.v.), the latter sometimes opening by a reservoir (r). The body contains in the ectoplasm myonema-fibrils which, by their contraction, withdraw the disc, and at the same time circular fibrils close the peristome over it. In the type-genus the pellicle is continued into a long, slender elastic stalk (s), of which the longitudinal myoneme fibrils of the ectoplasm converge to the stalk, and are prolonged into it as a spirally winding fibre, sometimes transversely striated.[175] The effect of the contraction of this is to pull the stalk into a helicoid spiral (like a coilspring), with the line of insertion of the muscle along the inner side of the coils, which is, of course, the shortest path from one end to the other (Fig. 60, B).
F . 60. Vorticella. A, expanded; B, stalk in contraction; c, eversible collar below peristome; cr, line of posterior ciliary ring; c.v, contractile vacuole; m, muscle of stalk; N, meganucleus; n, micronucleus; p, pharynx; r, reservoir of contractile vacuole; s, tubular stalk; u.m, undulating membrane in vestibule; v, hinder end of vestibule. E1 , E2 , two stages in binary fission; E3 , free zooid, with posterior wreath; F1 , F2 division into mega- and micro-zooids (m); G1 , G2 , conjugation; m, microzooid (Modified from Bütschli, from Parker and Haswell )
The members of the Vorticellidae are very commonly attached to weeds or to various aquatic Metazoa, each species being more or less restricted in its haunts. Vorticella, the type, is singly attached to a contractile stalk; fission takes place in the vertical plane, and one of the two so formed retains the original stalk, while the other swims off (Fig. 60, E1-E3), often to settle close by, so that the individuals are found in large social aggregates, side by side, fringing waterweeds with a halo visible to the naked eye, which disappears on agitation by the sudden contraction of all the stalks. Carchesium and Zoothamnium differ from Vorticella in the fact that the one daughtercell remains attached by a stalk coming off a little below the body of the other, so as to give rise to large branching colonies.
In Carchesium (Fig. 51) the muscular threads of each cell are separate, while in Zoothamnium they are continuous throughout the colony Epistylis has a solid, rigid stalk, and may give rise to branching colonies, which often infest the body of the Water-Fleas (Copepoda) of the genus Cyclops. Opercularia is characterised by
the depth of the gutter, the height of the collar, and the tapering downward of the elongated disc. Vaginicola, Pyxicola, Cothurnia, Scyphidia, all inhabit tubes, some of extreme elegance. Ophrydium is a colonial form, found in ponds and ditches, resembling Opercularia, but inhabiting tubes of jelly[176] that coalesce by their outer walls into a large floating sphere; it usually contains the green symbiotic Flagellate Zoochlorella. Trichodina is free, short, and cylindrical, with both wreaths permanently exposed, and is provided with a circlet of hooks within the aboral wreath. It is often parasitic, or perhaps rather epizoic, on the surface of Hydra (see p. 254), gliding over its body[177] with a graceful waltzing movement; it occurs also in the bladder and genito-urinary passages of Newts, and even in their body-cavity and kidneys.
II. S = T
Infusoria with cilia only in the young state,[178] without mouth or anus, but absorbing food (usually living Ciliates) by one or more tentacles, perforated at the apex; mostly attached, frequently epizoic, rarely parasitic in the interior of other Protozoa.
Acineta, Ehrb (Fig 61, 2); Amoebophrya, Koppen; Choanophrya, Hartog (Fig 62); Dendrocometes, St. (Fig. 61, 4); Dendrosoma, Ehrb. (Fig. 61, 9); Endosphaera, Engelm.; Ephelota, Str. Wright (Fig. 61, 5, 8); Hypocoma, Gruber; Ophryodendron, Cl. and L. (Fig. 61, 7); Podophrya, Ehrb. (Fig. 61, 1); Rhyncheta, Zenker (Fig. 61, 3); Sphaerophrya, Cl. and L. (Fig. 61, 6), Suctorella, Frenzel; Tokophrya, Bütschli.
This group, despite a superficial resemblance to the Heliozoa, show a close affinity to the Ciliata; the nuclear apparatus is usually double though a micronucleus is not always seen; the young are always ciliated, and the mode of conjugation is identical in all cases hitherto studied. Most of the genera are attached by a chitinous stalk (Fig. 61), continued in Acineta into a cup or "theca" surrounding the cell. The pellicle is firm, often minutely shagreened or "milled" in optical section by fine radial processes, whether superficial rods or the
expression of the meeting edges of radial alveoli is as yet uncertain. The pellicle closely invests the ectosarc, is continued down into a tubular sheath, from the base of which the tentacle rises, and upwards to invest the tentacle, and is even prolonged into its cavity in Choanophrya, the only genus where the tentacles are large enough for satisfactory demonstration. These organs may be one or more, and vary greatly in character. They may be (1) pointed for prehension, puncture, and suction (Ephelota, Fig. 61, 5); (2) nearly cylindrical, with a slightly "flared" truncate apex (Podophrya, Fig. 61, 1a); (3) filiform with a terminal knob; (4) "capitate" (Acineta, Fig. 61, 2); (5) bluntly truncate and capable of opening into a wide funnel for the suction of food[179] (Choanophrya, Fig. 62; Rhyncheta, Fig. 61, 3). Their movements, too, are varied, including retraction and protrusion, and a degree of flexion which reaches a maximum in Rhyncheta (Fig. 61, 3), whose tentacle is as freely motile as an elephant's trunk might be supposed to be were it as slender in proportion to its length. They are continued into the body, and in Choanophrya may extend right across it. In Podophrya trold the pellicle rises into a conical tube about the base of the tentacle, which is retracted through it completely with the prey in deglutition. In Dendrocometes, Dendrosoma, and Ophryodendron (Fig. 61, 4, 9, 7), the tentacles arise from outgrowths of the cell-body.
F . 61. Various forms of Suctoria. 1, a and b, two species of Podophrya; c, a tentacle much enlarged; 2, a, Acineta jolyi; 2, b, A. tuberosa, with four ciliated buds; in 6 the animal has captured several small Ciliata; 8, a, a specimen multiplying by budding; 8, b, a free ciliated bud; 9, a, the entire colony; 9, b, a portion of the stem; 9, c, a liberated bud. a, Organism captured as food; b.c, brood-cavity; bd, bud; c.vac, contractile vacuole; l, test; mg.nu, meganucleus; mi.nu, micronucleus; nu, nucleus; t, tentacle. (From Parker and Haswell, after Bütschli and Saville Kent )
The mechanism of suction is doubtful; but from the way particles from a little distance flow into the open funnels of Choanophrya, it may be the result of an increase of osmotic pressure. The external pellicle of the tentacles is marked by a spiral constriction,[180] which may be prolonged over the part included in the sheath. The endosarc is rich in oil-drops, often coloured, and in proteid granules which sometimes absorb stains so readily as to have been named "tinctin bodies." It usually contains at least one contractile vacuole.
In Dendrocometes (and perhaps others) the whole cell may become ciliated, detach itself and swim off; this it does when its host
(Gammarus) moults its cuticle.
In fission or budding we have to distinguish many modes. (1) In the simplest, after the nuclear apparatus has divided, the cell divides transversely; the distal half acquires cilia and swims off to attach itself elsewhere, while the proximal remains attached. The tentacles have previously disappeared and have to be formed afresh in both. (2) More commonly fission passes into budding on the distal face; a sort of groove deepens around a central prominence which becomes the ciliated larva (Fig. 62, em); the tentacles of the "parent" are retained. This process passes into (3) "internal budding," where a minute pit leads into a bottle-shaped cavity.[181] (4) Again, the budding may be multiple, the meganucleus protruding a branch for each bud, while the micronucleus, by successive divisions, affords the supply requisite. Sphaerophrya (Fig. 61, 6) and Endosphaera multiply freely by fission within their Ciliate hosts, and were indeed described by Stein as stages in their life-cycle. Conjugation of the same type as in most Ciliates has been fully worked out in Dendrocometes alone, by Hickson,[182] who has found the meganuclei (though destined to disorganisation) conjugate for a short time by the bridge of communication before the reciprocal conjugation of the micronuclei.
We have referred to the endoparasitism of two genera. Amoebophrya lives in several Acanthometrids, and in the aberrant Radiolarian Sticholonche (see p. 86). The attached species are some of them indifferent to their base; others are only found on Algae, or again only epizoic on special Metazoan hosts, or even on special parts of these. Thus Rhyncheta is only found on the couplers of the thoracic limbs of Cyclops, and Choanophrya on the ventral surface of its head and the adjoining appendages.
F . 62. Choanophrya infundibulifera. A, adult; B-D, tentacles in action in various stages; E, tentacle at rest; F, young, just settled down, a, a, a, Tentacles in various stages of activity; c, central cavity; c.v, contractile vacuole; em, ciliated embryo showing contractile vacuole and nucleus; f, spiral ridge; m, muscular wall of funnel; n, nucleus; tr, opening of funnel (AD, F, modified after Zenker; E, original )
We owe our knowledge of this group to the classical works of Ehrenberg, Claparède and Lachmann, Stein, R. Hertwig, and Bütschli. Plate has shed much light on Dendrocometes, and Hickson has studied its conjugation. Ischikawa[183] has utilised modern histological methods for the cytological study of Ephelota bütschliana. René Sand has written a useful, but unequal, and not always trustworthy monograph of the Order,[184] containing an elaborate bibliography.
PORIFERA (SPONGES)
BY
IGERNA B. J. SOLLAS, B.S . (L .)
Lecturer on Zoology at Newnham College, Cambridge.
CHAPTER VII
PORIFERA (SPONGES)[185]
INTRODUCTION HISTORY DESCRIPTION OF H A L I C H O N D R I A P A N I C E A AS AN EXAMPLE OF BRITISH MARINE SPONGES AND OF E P H Y D A T I A F L U V I A T I L I S FROM FRESH WATER DEFINITION POSITION IN THE ANIMAL KINGDOM.
Sponges occupy, perhaps, a more isolated position than any other animal phylum. They are not only the lowest group of multicellular animals, but they are destitute of multicellular relatives. They are all aquatic and—with the exclusion of a few genera found in fresh water —marine, inhabiting all depths from between tide marks to the great abysses of the ocean. They depend for their existence on a current of water which is caused to circulate through their bodies by the activity of certain flagellated cells. This current contains their food, it is their means of respiration, and it carries away effete matters. Consequently sponges cannot endure deprivation of oxygenated water except for short periods, and only the hardiest inhabit regions where the supply is intermittent, as between tide marks. This also renders useless attempts to keep specimens in tanks, unless the water is frequently renewed.
The outward appearance of sponges has an exceptionally wide range, so that it is difficult to give a novice any very definite picture of what he is to expect when searching for these animals. This diversity is in part due to the absence of organs of sufficient size to determine the shape of the whole or limit its variation, that is to say, the separate organs are of an order of size inferior to that of the entire body. The animals are fixed or lie loose on the sea bottom; there are in no case organs of locomotion, and again no sense-organs, no segregated organs of sex, and as a rule no distinction into axis and lateral members. It is by these negative characters that the collector may easily recognise a sponge.
History.—Sponges are, then, in many of their characters unique; and they present a variety of problems for solution, both of special and general interest, they are widely distributed in time and space, and they include a host of forms. It therefore causes no little surprise to learn that they have suffered from a long neglect, even their animal nature having been but recently established. Though known to naturalists from the time of Aristotle, sponges have been left for modern workers as a heritage of virgin soil: it has yielded to them a rich harvest, and is as yet far from exhausted.
The familiar bath sponge was naturally the earliest known member of the phylum. It is dignified by mention in the Iliad and in the Odyssey, and Homer, in his choice of the adjective "full of holes," πολύτρητος, shows at least as much observation as many a naturalist of the sixteenth and seventeenth centuries. Aristotle based his ideas of sponges entirely upon the characters of the bath sponge and its near allies, for these were the only kinds he knew With his usual perspicuity he reached the conclusion that sponges are animals, though showing points of likeness to plants.
The accounts of sponges after Aristotle present little of scientific interest until the last century. Doubtless this is in part due to the absence of organs which would admit of dissection, and the consequent necessity of finer methods of study Like other attached
forms, sponges were plant or animal as it pleased the imagination of the writer, and sometimes they were "plant animals" or Zoophyta: those who thought them animal were frequently divided among themselves as to whether they were "polypous" or "apolypous." An opinion which it is somewhat difficult to classify was that of Dr. Nehemiah Grew,[186] who says: "No Sponge hath any Lignous Fibers, but is wholly composed of those which make the Pith and all the pithy parts of a Plant, ... So that a Sponge, instead of being a Zoophyton, is but the one-half of a Plant."
Sponges figure in herbals beside seaweeds and mushrooms, and Gerarde says:[187] "There is found growing upon rockes near unto the sea a certaine matter wrought together of the foame or froth of the sea which we call Spunges ... whereof to speak at any length would little benefit the reader ... seeing the use thereof is so well known." About the middle of the eighteenth century, authors, especially Peyssonnel, suggested that sponges were but the houses of worms, which built them much as a bee or wasp builds nests and cells. This was confuted by Ellis in 1765,[188] when he pointed out that the sponge could not be a dead structure, as it gave proof of life by "sucking and throwing out water." To Ellis, then, is due the credit of first describing, though imperfectly, a current set up by sponges. He mentions that Count Marsigli[189] had already made somewhat similar observations.
It was not till 1825 that attention was again turned to the current, when Robert Grant approached the group in a truly scientific manner, and was ably supported by Lieberkühn. It would be impossible to do justice to Grant in the brief summary to which we must limit ourselves. The most important of his contributions was the discovery that water enters the sponge by small apertures scattered over the surface, and leaves it at certain larger holes, always pursuing a fixed course. He made a few rough experiments to estimate the approximate strength of the current, and, though he failed to detect its cause, he supposed that it was probably due to ciliary action. Grant's suggestion was afterwards substantiated by
Dujardin (1838), Carter (1847), Dobie (1852), and Lieberkühn (1857). These five succeeded in establishing the claims of sponges to a place in the animal kingdom, claims which were still further confirmed when James-Clark[190] detected the presence of the protoplasmic collar of the flagellated cells (see pp. 171, 176). Data were now wanted on which to base an opinion as to the position of sponges within the animal kingdom. In 1878 Schulze[191] furnished valuable embryological facts, in a description agreeing with an earlier one of Metschnikoff's, of the amphiblastula larva (p. 226) and its metamorphosis. Then Bütschli[192] (1884) and Sollas[193] on combined morphological and embryological evidence (1884) concluded that sponges were remote from all the Metazoa, showing bonds only with Choanoflagellate Protozoa (p. 121). This the exact embryological work of Maas, Minchin, and Delage has done much to prove, but it has to be admitted that unanimity on the exact position of the phylum has not yet been attained, some authorities, such as Haeckel, Schulze, and Maas still wishing to include sponges in the Metazoa.
In this short history we have been obliged to refer only to work helping directly to solve the problem of the nature of a sponge, hence many names are absent which we should have wished to mention.
Halichondria panicea.
One of the commonest of British sponges, which may be picked up on almost any of our beaches, and which has also a cosmopolitan distribution, is known by the clumsy popular name of the "crumb of bread sponge," alluding to its consistency; or by the above technical name, with which even more serious fault may be found.[194]
In its outward form H. panicea affords an excellent case of a peculiarity common among sponges. Its appearance varies according to the position in which it has lived. In fact, Bowerbank
remarks that it has no specific form. It may grow in sheets of varying thickness closely attached to a rock, when it is "encrusting," or it is frequently massive and lying free on the sea bottom; again, it may be fistular, consisting of a single long tube, or it may be ridge-like, apparently in this case consisting of a row of long tubes fused laterally. In this last form it used to be called the "cockscomb sponge," having been taken for a distinct species.
Bidder has proposed to call the different forms of the same species "metamps" of the species. Figures of the metamps of H. panicea will be found in Bowerbank's useful Monograph.[195]
The colour of the species is as inconstant as its form, ranging from green to light brown and orange. MacMunn concludes from spectroscopic work that H. panicea, contains at least three pigments, a chlorophyll, a lipochrome, and a histohaematin.[196] Lipochromes vary from red to yellow, chlorophyll is always associated with one or more of them. Histohaematin is a respiratory pigment. Proof has not yet been adduced that the chlorophyll is proper to the sponge and is not contained in symbiotic algae.
In spite of all this inconstancy H. panicea, is one of the most easily determined species. It is only necessary to dry a small fragment, including the upper surface; a beautiful honeycomb-like structure is then visible on this surface, and among British sponges this is a property peculiar to the species (Bowerbank). Whatever the form of the sponge, one or more large rounded apertures are always present on the exterior; these are the "oscula." In the encrusting metamp the oscula are flush with the general surface, while in the other cases they are raised on conical projections; fistular specimens carry the osculum at the distal end, and the cockscomb has a row of them along its upper edge. Much more numerous than the oscula are smaller apertures scattered over the general surface of the sponge, and known as "ostia."
F 63 —Portion of the surface of H panicea, from dried specimen A, natural size; B, magnified. The large shaded patches are ostia.
If the sponge be placed in a shallow glass dish of sea water the function of the orifices can be made out with the naked eye, especially if a little powdered chalk or carmine be added to the water. If the specimen has been gathered after the retreating tide has left it exposed for some time, this addition is unnecessary, for as soon as it is plunged into water its current bursts vigorously forth, and is rendered visible by the particles of detritus that have accumulated in the interior during the period of exposure and consequent suspended activity The oscula then serve for the exit of currents of water carrying particles of solid matter, while the entrance of water is effected through the ostia.
Sections show that the ostia lead into spaces below the thin superficial layer or "dermal membrane"; these are continued down into the deeper parts of the sponge as the "incurrent canals," irregular winding passages of lumen continually diminishing as they descend. They all sooner or later open by numerous small pores —"prosopyles"—into certain subspherical sacs termed flagellated chambers. Each chamber discharges by one wide aperture —"apopyle"—into an "excurrent canal." This latter is only distinguishable from an incurrent canal by the difference in its mode of communication with the chambers.
F . 64.—H. panicea: the arrows indicate the direction of the current, which is made visible by coloured particles. (After Grant.)
The excurrent canals convey to the osculum the water which has passed through the ostia and chambers. All the peripheral parts of the sponge from which chambers are absent are termed the "ectosome," while the chamber-bearing regions are the "choanosome."
The peculiar crumb-of-bread consistency is due to the nature of the skeleton, which is formed of irregular bundles and strands of minute needles or spicules composed of silica hydrate, a substance familiar to us in another form as opal: they are clear and transparent like glass. They are scattered through the tissues in great abundance.
The classes of cellular elements in the sponge are as follows: Flattened cells termed "pinacocytes" cover all the free surfaces, that is to say, the external surface and the walls of the excurrent and incurrent canals. The flagellated chambers are lined by "choanocytes" (cf. Fig. 70, p. 176); these are cells provided at their inner end with a flagellum and a collar surrounding it. They resemble individuals of the Protozoan sub-class Choanoflagellata, and the likeness is the more remarkable because no other organisms are known to possess such cells. Taken together the choanocytes constitute the "gastral layer," and they are the active elements in producing the current. The tissue surrounding the chambers thus lying between the excurrent and incurrent canals consists of a gelatinous matrix colonised by cells drawn from two distinct sources. In the first place, it contains cells which have a common origin with the pinacocytes, and which together with them make up the "dermal
