214 Prof. H. James-Clark on the Sponglaa ciliatse. 



tions was 2.30 p.m. By 2.35 p.m. (fig. 54) tlie larger fla- 

 gella (Jl) had separated still further, and the smaller cilium 

 had split into two {Ji^) very conspicuous filaments, as yet, 

 however, attached to a common point of the body. From this 

 time forth to the completion of the process of fissigemmation 

 all of the cilia kept up a slow vibration, in which they undu- 

 lated from base to tip with a sort of snake-like motion. By 

 2.45 P.M. (fig. 55) the body had become quite appreciably 

 broader than long, the contractile vesicles {cv) were widely 

 separated, and the smaller cilia had left between them a con- 

 siderable space, and each one had approximated quite near to 

 the base of a larger flagellum. At 2.50 p.m. (fig. 5G) the 

 body had become nearly twice as broad as long, and the space 

 (e^) between the two pairs of cilia was nearly twice as great 

 as in the last phase, and considerably depressed in the middle, 

 so that the body had a broadly cordate outline. By 2.52 P.M. 

 (fig. 57) the posterior end of the body (at a point a little to 

 one side of the spot where it was attached to the pedicel) was 

 also slightly indented, so that in outline it presented a guitar- 

 shaped figure, each rounded half of which bore a pair of un- 

 equal cilia, and contained a conti-actile vesicle. In one minute 

 more the contraction had increased to such an extent that the 

 body was divided about halfway through (fig. 58). By 2.54 

 P.M. (fig. 59) the animal had a dumb-bell shape, and the 

 pedicel {jyd) was attached to one of the segments near the 

 point of constriction. Still the process went on very rapidly, 

 and by 2.55 p.m. (fig. 60) the new bodies were widely sepa- 

 rated, but still attached to each other by a mere thread. At 

 3 P.M. (fig. 61) the body which was attached to the pedicel 

 was left alone, and its companion swam away to seek a new 

 attachment and build up its stem. 



" To the last moment the hyaline envelope remained about the 

 segments, and in fact so long afterwards that time and circum- 

 stances did not allow me to ascertain its final disposition. I 

 would remark, however, that when the ovate bodies of the 

 half-grown monads (fig. 49) are contracted temporarily into a 

 globular shape, they appear identical (excepting that they 

 lack the hyaline envelope) with these recently fissed forms. 

 In all probability, therefore, the latter lose their envelope and 

 assume the shape of the former. 



" As to the development of the stem, I think it quite cer- 

 tain that it grows out from the posterior end of the body. The 

 best proof of this is, that I have frequently found a monad 

 (especially in the condition of the one which I described above 

 as breaking loose from its companion) nearly sessile upon a 

 clean spot, and attached by a very short, faint, film-like 



