62 H. M. WOODCOCK. 



Gregariues (Berndt [1]), etc. The first indication of pre- 

 cocity is perhaps seen in Zygocj'stis, where the individuals 

 always associate as soon as they become adult trophozoites. 



Diplocystis. — The development of neogamy to an ad- 

 vanced degree, along parallel but quite independent lines, is 

 well shown by Diplocystis on the one hand and Diplodiua 

 and Cystobia on the other. In the case of Diplocystis 

 major, a coelomic parasite of the cricket (Gryllus), Cnenot 

 (loc. cit.) found that the Gregarines can grow to a certain size 

 alone (up to *2 mm. in diameter) but not to their full extent, 

 i. e. to become sporonts; couples, however, attain to a diameter 

 of 1'3 mm. Still, the mutual adherence is very feeble — the two 

 individuals being easily separated — and, moreover, often in- 

 discriminate, several Gregarines of different ages being at 

 times grouped together (see Cuenot^s fig. 40, PL 20), some of 

 which have to be got rid of as de trop . A further advance 

 is seen in D. minor, in which the longest diameter of a 

 couple is, at most, '6 mm. Here "pairing" takes place 

 much earlier in life. Solitary individuals larger than 30 fi 

 are never met with, and, indeed, association is sometimes 

 accomplished before the parasites have passed from the gut- 

 wall into the coelom. Moreover, the union is closer and more 

 definite, the two individuals becoming enclosed in a common 

 membrane, which may be looked upon as an earlj^-formed 

 ectocyst. Nevertheless, inside this, the double nature of the 

 syzygy is distinctly to be seen, there being an obvious 

 V-shaped constriction all round the middle, marking the 

 plane of junction, and only slightly less prominent than in 

 my fig. 3 (see Cuenot, fig. 41, or Minchin [26], fig. 22). 



Next comes D. sclin eider i, the trophic phase of which I 

 have above re-described. While the association in this para- 

 site may be, apparently, sometimes more precocious and 

 intimate than in D. minor,^ an advance upon the condition 



* In none of tlie individuals of D. schneideri which I e,\aiiiiucd was the 

 septum absent. Kunstlcr, liowevcr, in liis fig. 16 (loc. cit.), has drawn a 

 small exami)le, still attached to the intestinal wall by the peritoneal epithelium, 

 which a])pcars to lack a septum. Cuenot (loc. cit.) is of the opinion that 



