LIFE-CYCLE OF " CYSTOBIA " IRREGULAEIS (mINCH.). 61 



size of the spore averages 14 ^ x 6 //. There is probably 

 no inner (endospore) funnel open to the exterior ; moreover, 

 no sign of a pUig is visible. Sporozoites possess (in all 

 instances observed) a central nucleus, square or rounded. 

 Habitat: respiratory trees and body-cavity of Cucumaria 

 pentactes and C. planci. 



Family, Urosporidte; genus, Cystobia, Ming., 1891. 



The exospore at the basal end of the spore is prolonged 

 into a flat process, like a lance-head. 



C. bolothurias (Schn). Not having had an opportunity 

 of personally studying this parasite, I am unable to add to 

 the definition above given (p. 3). 



The consideration of these neogamous Gregarines affords 

 an excellent opportunity for a general discussion of the 

 phenomenon of association, as it is known to occur iu the 

 oi'der. 



(10) PiiECOCious Association or Neogamy, 



(ft) Comparative account of the principal varia- 

 tion s i n t h e m a n n e r a n d t i m e o f association. 



We may commence by following the gradual increase in 

 the precocity and intimacy of the "pairing" as exemplified 

 by different forms. Leaving out of account, for the present, 

 the "chains" formed by certain Gregarines, which are pro- 

 bably often broken and differently reconstituted, and whose 

 significance is not fully understood, we have, in the simplest 

 cases, a union of two adult trophozoites immediately prior to 

 encystment and the commencement of sporulation (Lankes- 

 teria, Monocystis, Stylorhynchus, etc.). The dividing 

 partition separating the two associates does not usually break 

 down until nuclear division is well advanced. Next, we get 

 the binary syzygies of most adult Gregarines, which proceed 

 to encystment after remaining attached to each other for 

 some time, as in Gregarina cuneata and other meal-worm 



