OBSERVATIONS ON THE GREGARINES OF HOLOTHURIANS. 303 



so that not much stress can be laid on this point for classi- 

 fication. The spores of Syncystis lack the characteristic 

 funnel of the spores of our Gregarines, and the caudal process 

 of the latter can be in no way homologised (even if it were a 

 constant phenomenon, which is not the case) with the bristles 

 of the spore of Syncystis. Hence I think we are justified 

 in concluding that the Gregarines of Holothurians have no 

 affinity whatever with the family Syncystidse. 



On the other hand, in regard to their double nature, these 

 Gregarines have a considerable resemblance to the remarkable 

 Diplocystis Schneideri described by Kunstler (12) from 

 the body-cavity of Periplaneta americana. This form 

 lives in a conjugated condition, and " presents normally the 

 aspect of two monocystid Gregarines in syzygy, and preparing 

 for encystment," p. 45 (=21). Each half, however, has a 

 membrana propria, but the whole is surrounded by a general 

 membrane which passes from the one to the other without 

 penetrating their plane of separation. But in the very young 

 stage (pp. 26, 27, pi. ix, fig. 16) it occurs attached to the 

 digestive tract of the Periplaneta in a serous sac, contains 

 two nuclei which differ in structure from one another, and 

 is not divided by a septum. The conjugation takes place 

 very early in the life-history, almost immediately after the 

 intra-cellular phase, p. 61 (= 37), figs. 18, 19. According to 

 M. Kunstler, p. 62 (= 38), the conjugation does not appear 

 to be the result of union of two individuals primitively separate, 

 but a single intra-cellular form divides, to afterwards fuse com- 

 pletely and then to separate again. I am therefore rather 

 inclined, on a priori grounds, to doubt if these observations 

 are quite correct ; it seems to me more probable that the little 

 couples shown in Kunstler^s fig. 18 are derived from two 

 separate intra-cellular individuals which he has overlooked, as 

 the best of observers might very easily do. In any case I 

 would point out the striking parallel between Kunstler's fig. 

 16 and my fig. 20. 



The spores of Diplocystis are oval or spherical without 

 any appendages. The sporozoites, eight in number, cross one 



