LIKE-OYOLE OF "OYSTOBIA" IRREGULARIS (mINCH.). G3 



found in that species is cliiefly noticeable in the modification 

 of the encystment-process (see above, p. 27). Nothing of 

 this kind is mentioned by Cueuot in his description of 

 J), minor. Judging from this author's figures, the formation 

 of the ectocyst there resembles the manner in which it occurs 

 in the ordinary process of encystment, as the spherical shape 

 of the couple is much more cyst-like and the ectocyst does 

 not appear to enter at all into the plane of junction. D. 

 minor represents, therefore, a condition intermediate be- 

 tween ordinary encystment and the secreting of an early 

 ectocyst at all points of the body, closely following the adult 

 form, which is thereafter retained, as in D. schneideri. 



Thus we can conveniently arrange the different species of 

 Diplocystis in a series, as follows : 



(1) D. majoi', in which precocious association is already 

 necessary if the trophozoites are to become full grown, but 

 its occurrence is haphazard and promiscuous, and the actual 

 attachment only feeble. 



(2) D. minor, in which neogamy occurs early in life, and 

 its permanence is assured by precocious encystment. 



(3) D. schneideri, in which the ectocyst-formation is 

 modified and distinctly adapted to the trophic phase of the 

 life-history. 



Diplodina and Cystobia. — In these two genera we 

 find the most advanced condition of neogamy known among 

 Gregarines. 



In D. irregularis this extremely early and intimate 

 joining appears to be in process of development. Many 

 individuals — probably the majority — are content to unite so 

 as to acquire at length the appearance of one septate but 



Kunstler must have overlooked one iu this case. The septum when present 

 is, however, so obvious, and the structure of the particular specimen was, for 

 the rest, so clearly seen, that I do not think this view altogether certain. It 

 is not necessary, moreover, to suppose tliat the septum is invariably present. 

 Quite possibly in certain, perhaps exceptional, instances neogamy in D. 

 schneideri may be so precocious and intimate that no partition separates the 

 two associates, just as is often the case in Diplodina irregularis (see 

 next page). 



