314 H. JAMES-CLARK ON THE AFFINITIES OF SPONGES. 



it ; as one may see by comparing figures 8 and 47 with each other. It also frequents the same 

 habitat as Anthophjsa, where it is quite abundant, and readily recognized, when one has be- 

 come familiar with it, even under as low a magnifying power as two hundred diameters. 

 The greater number of individuals are found attached singly (figs. 9 and 24 a ) or in twos to a 

 slender peduncle (pd) ; but often three or four constitute a colony. A group of these monads, 

 seated on their short pedicels (fig. 8 pel 2 ), and the latter arising from a nearly common point at 

 the end of a long, slender peduncle (fig. 8 pd), might be designated, in botanical parlance, as 

 umbellate. Very seldom are more than four or five bodies assembled in one colony, but 

 occasionally as many as eight (fig. 7) are united in a single umbel. They bear the same re- 

 markable relation to each other and to the main stem (pd) that we find in Anthophysa, that 

 is to say, the arcuate flagelluin (/) of every member of the group curves backwards to- 

 wards the base of the common peduncle (pd) ; and consequently the rest of the organism of 

 each one holds a corresponding position. When there are but three or four in a colony the 

 longer axis of each monad usually diverges at an angle of not more than thirty or thirty- 

 five degrees from the axis of the main stem, but when the number is greater the divergence 

 is also greater, and frequently amounts to seventy or eighty degrees. Oftentimes it will be 

 observed that several of a group of bodies are attached in pairs (figs. 21, 22) to the pedi- 

 cels, instead of each being possessed of a support of its own. This, as will be explained 

 more fully under the head of fissigemmation, arises from an incompleteness of the self-divis- 

 ion of which the pairs are the several resultants ; and it will be noticed also that they are 

 smaller than those which arise singly from the common peduncle. 



The usual form of the body is an oblique oval (figs. 25, 26, 27,) which is twice as long as 

 it is broad ; but in old individuals, which are about to undergo self-division, the shape is very 

 broadly oval (fig. 24 a ), and its o:ie-sidedness is not very conspicuous. The same may be 

 said of specimens which have lived for a while in stale water, and have lost nearly all their 

 yellow color (fig. 24). Posteriorly it tapers, more or less abruptly, into the pedicel (figs. 25, 

 26, 27, pd 2 ) ; but anteriorly it is slightly constricted (b 2 ) a short distance behind the front, 

 and thence projects in the form of a low. truncate cone (fig. 24* fr). From the constriction 

 (b 2 ) there projects, in direct continuation of the epidermis of the body proper, a very high 

 membranous, campanuUform collar (b, b 1 ), presenting, on the whole, an appearance as if the body 

 were seated in the lower half of a deep, urceolate calyx. That this collar is not the upper 

 portion of an urceolus in any sense of the term may be demonstrated in two ways, at least. 

 In the first place, it is highly flexible and retractile ; as it occasionally shows itself to be, 

 either by narrowing its aperture almost to absolute closure (fig. 24, b), or by reducing its 

 height to a small fraction of its greatest altitude, — as seen in fig. 27, b, — and then extend- 

 ing itself again, within a few seconds, by a direct protrusion, (fig. 26, b) to its original pro- 

 portions (fig. 25, b). In the second place, it divides longitudinally, like the rest of the body 

 when self division occurs (figs. 11-22), a process in which no genuine calicle was ever known 

 to be concerned. In an adult state (figs. 8, 11, 24 a , 25) it is slightly constricted by a gradual 

 incurvature extending from the base (fig. 24 a , P) to the distal margin (P) ; but frequently, 

 and apparently always just before self-division takes place, its sides bulge slightly out- 

 ward (fig. 11, b). Taking all these things into consideration, therefore, it is perfectly clear 

 that this infusorian is not a calyculate form, but one of those mimetic shapes which occa- 

 sionally deceive the eye and puzzle the observer, until he becomes familiar with their various 

 phases of growth and development. 



