46 H. M. WOODCOCK. 



somes, as desciibecl iu the case of Monocystis, and also by 

 Leger for Sty lorhyuclius and Brasil for Urospora. 



Independent division of tlie centrosomes. — Avery 

 interesting peculiarity of the division centres in C. irregu- 

 laris must be mentioned — namely their occurrence alone and 

 quite separate from the nuclei. For it is certain that isolated 

 centrosomes do at this period occur, and, indeed, in many of 

 my sections they are not at all uncommon. One of them is 

 figured at g, and it will be observed that it is quite similar 

 to those in relation with the sexual nuclei. Equally certain 

 is it that these isolated centrosomes also divide by themselves; 

 h, i, and J show this distinctly. In all cases, whether of single 

 or dividing ones, I have carefully examined neighbouring 

 sections of the series, but without finding any trace of a 

 nucleus in connection with them. This independence of 

 certain division-centres is an unusual circumstance, and, so 

 far as I am aware, has not hitherto been described in the case 

 of Gregarines.^ 



It may, perhaps, be suggested, Does not the appearance seen 

 at j represent, rather, the final stage in nuclear division, the 

 two halves remaining attached only by a delicate, drawn-out 

 thread ? If this were so, it would imply that practically all 

 the chromatin of the two daughter-nuclei had become (tem- 

 porarily) united with the two centrosomes. This is exactly 

 what Cuenot describes and figures (loc. cit., fig. 55 (/) in the 

 mitoses of Diplocystis minor; and, as a result, the grain 

 at the centre of each attraction-sphere (consisting of centro- 

 some plus the chromatin of a daughter-nucleus) is very greatly 

 enlarged as compared with the normal size of a centrosome 

 when associated with a resting-nucleus (fig. 55 a — c). The 

 centrosomes in my fig. 51^, on the contrary, exhibit no per- 

 ceptible differences, whether of size or staining pro])ertics, 

 from those above described in close connection with the sexual 

 nuclei. Moreover, the aspect of a daughter-nucleus immediately 

 after separation (iig. 51/', already described), is quite different. 



1 It is not an uncommon fc;ituic in spcrmrito^fncsis, however, for wcll- 

 dllTcrentiatcd kinetic centres to divide b^ llieni selves. 



