LIFE-CYCLE OE " CYSTOBTA " IRREGULAEIS (mFNCH.). 85 



neogamous Grregarine^ or one in wliicli precocious association 

 occurs. lu D. irregularis the two associates are sometimes 

 separated by a distinct septum and sometimes not^ this being- 

 dependent upon tlie time of union. In either case^ however, 

 the adult couple — when the union is completed — presents 

 superficially almost the aspect of a Monocystid Gregarine. 

 In D. minchinii there is never any septum, the union of 

 the two cytoplasms beiug intimate. In this species the 

 association is lateral, while in D, irregularis it is terminal. 



The general appearance of Diplocystis schneideri 

 agrees with Kunstler's description. 



I have occasionally met with instances of triple association 

 in both species of Diplodina, and also in Diplocystis. 



(5) There is a marked absence of differentiation in the 

 peripheral region of the body of Diplodina. The general 

 cytoplasm is limited by a delicate membrane, but there is no 

 appearance either of ectoplasm or of myocyte-fibrlllas. In 

 strong contrast is the firm and definite ectoplasmic layer 

 in Diplocystis schneideri. Moreover, in this parasite 

 the couple is always enclosed in an investing membrane, 

 comparable to an early-formed ectocyst, which is laid down 

 in the form of the couple and specially thickened around the 

 plane of junction. 



The cytoplasm in Diplodina has a quite typical gregari- 

 noid structure. The nucleus possesses a distinct chromatic 

 reticulum, in which is slung or suspended a single karyosome. 

 With growth, the karyosome becomes very vacuolated, the 

 smaller vacuoles running together to form two or three large 

 ones, the contents of which are manifestly passed out into 

 the nucleoplasm. I regard this process, not as one of excretion, 

 but as a reinforcement of the chromatin of the nucleoplasm. 



(6) The process of eucystment in D. irregularis is very 

 slight. In the majority of cases there is no ectocyst-forma- 

 tion whatever, and the limiting membrane serves as a delicate 

 endocyst. The most obvious cyst membrane, indeed, is the 

 peritoneal epithelium enclosing* the cyst, which persists 

 after the endocyst has broken down and disappeared. In 



