LIFE-CYCLE OF " CYSTOBIA " lEHEGULARLS (mINCH.). 23 



specimen of the common cockroacli, Peri planet a orien- 

 tal is, and were all in a practically similar condition, viz. that 

 of trophozoites of vai-ying age and size. 



The animals ag-ree, on the whole, with Knnstler's descrip- 

 tion as regards size, shape, and general appearance. I found 

 the length of a couple to vary from 1*2 ram. up to nearly 

 1*7 mm., while the greatest breadth varied from '6 mm. to 

 1 mm. None of those measured were quite as large as the 

 largest Kunstler found, which attained 2 mm. in length, but 

 since the size of these ccelomic Gregarines varies consider- 

 ably, not much stress need be laid on that point. Figs. 21 

 and 22 show couples of large and small size respectively, that 

 in fig. 21 being seen whole, while fig. 22 represents a section 

 which happens to pass through the nucleus of one member of 

 the pair. An adult syzygy is distinctly bilobed ; and this was 

 the case with all the individuals examined. Moreover, a well- 

 marked septum is invariably present.^ The couple is always 

 longer than broad, more or less dumbbell-shaped in fact, and 

 never rounded or spherical as in D. minor (vide Cuenot, loc. 

 cit.). Further, the much larger size to which they grow and 

 the structure of the nucleus — which is, in general, quite like 

 Knnstler's description and figures — also tend to remove my 

 Gregarines from this species of Cuenot's. Each couple has a 

 general or " common " membrane completely investing it 

 [i.m., fig. 21) , which is quite unrepresented in the tropho- 

 zoites of Cystobia. In this respect my parasites agree 

 equally with D. minor and 1). schneideri, and differ from 

 D. major (see below, p. 62). The above facts prove without 



^ Unfortunately, many of the specimens showed the appearance drawn in 

 fig. 23. Wliether fixed by corrosive and acetic, Flemming, or absolute alcohol, 

 most of the ])rotoplasm (ihe endoplasm) was usually found more or less 

 retracted, leaving only the ectoplasm and delicate cuticle in close connection 

 with the investing membrane to show the true size and shape of tiie animal 

 when alive. Under a low power, of course, these together appear extremely 

 thin, compared with the relatively huge mass of endoplasm. The apparent 

 thickness of the septum in this lig. is due to its being viewed slightly out of 

 the plane in which it lies; I generally found this appearance in such shrunk 

 specimens. 



