H. JAMES-CLARK ON THE AFFINITIES OF SPONGES. 323 



greatest height it equals that of the body, and always terminates in a smooth edge. Its 

 plasticity is also equal to that of the marine species. In one instance, when the animal was 

 disturbed by a predaceous Rotifer, its whole body quickly retracted, and the collar totally 

 disappeared, as if melted down with great rapidity ; but soon after protruded slowly, at first 

 with a broad base (fig. 37 d , b), and then rapidly narrowed at the latter point and assumed its 

 usual proportions. 



The fiagellwm (fl) differs from that of S. marinus, both in proportions and deportment. It 

 is usually rigid and projects considerably beyond the collar when the latter is at its greatest 

 height. It has a decided arcuate figure, with a uniform thickness throughout, excepting 

 near the base, which tapers rapidly from the low cone in the middle of the front. Its apex 

 moves with quite gentle, spasmodic twitches, and the whole becomes flexible (fig. 37 b ,./7) 

 when faeces are ejected, or some undesirable particle enters the area within the collar. 



The mouth was not actually seen ; but that it exists somewhere about the base of the 

 flagellum was sufficiently demonstrated by seeing minute particles of food thrown by the 

 latter organ against the front, and rapidly disappear there. The anus (fig. 37, a) certainly 

 opens within the same area, as particles of considerable size were seen to make their exit 

 at the base of the flagellum. No digestive vacuoles were noticed, although the body was 

 often found filled with food. 



The contractile vesicles (cv) usually amount to three or four, and rarely to five in number ;^or 

 there are two very large ones, which occupy nearly the whole breadth of the body (fig. 37 a ). 

 They occur in all parts of the body except its neck, and beat with a sluggish systole about 

 at the same rate as those of Codosiga (§ 6). 



The calyx (c, c l ) has very much the same proportions as the body over which it is fitted as 

 if upon a mould. Its posterior half (c) is globular, and is attached at its hindermost, axial 

 termination to the point of support. Although hundreds of specimens of this species were 

 observed, not one of them had a pedicel. The anterior half tapers, like the thick neck of an 

 urn, from the posterior one to one third its diameter, and then rapidly widens and terminates 

 with a flaring, smooth-edged aperture (c 1 ), which is about twice as wide as its narrowest por- 

 tion. The margin usually is exceeded by the projecting head, so that the former may be seen 

 quite readily as a distinct ring behind the circular edge of the front from which the collar 

 rises. The empty calicles (fig. 37°) were found very frequently, and so nearly identical in 

 form with those of the living body that they must have possessed considerable rigidity. 

 That they are, however, to a certain degree flexible and plastic, was shown on one occasion 

 when the body and neck suddenly retracted and swelled laterally (fig. 37 d ) to an extent 

 which was considerably beyond the usual breadth of the calyx and its neck, and then 

 returned to its former shape and proportions. 



§ 10. Leucosolenia (Grantia) botryoides, Bowerbank. 



(Plate IX., figs. 40-44. Plate X., fig. 64.) 



If I were now to describe merely the congregated monads of this compound animal with- 

 out giving it a name, any one who had already become acquainted with the structure of 

 Codosiga (§ 6) would set down the first as a colonial, massive form of the latter. In fact, 

 a glance at a figure of a free swimming individual (fig. 23) of Codosiga, in one of its 

 numerous attitudes, and then a momentary inspection of the monad (figs. 42, 43, 44) of this 



