SOME OBSERVATIONS OX A NEW GREGAETNE. 281 



thus thoroughly equipped for their part in the ceremony of 

 division. 



It will be noticed that, except in fio-. 15, where the vesicles 

 attain their maximum development, there is no true striation 

 shown distal to the polar aggregation; in other words, 

 although the spindle-fibres are throughout very distinct, the 

 centrosome element is not. This, again, suggests a bearing 

 on the oi-igin of the centrosome. On the one hand, as Dobell 

 (8) points out, we have a binucleate condition held as the 

 starting-point in the development of the centrosome; on the 

 other there are observers, such as R. Hertwig-, who believe 

 the centrosome to be a specialisation of the central spindle, so 

 that the spindle in the Protozoa is equivalent to centrosome + 

 spindle of the Metazoa. Without Avishing to claim originality 

 for the suggestion, I may say that the first division figures of 

 Metamera schubergi have all along pointed forcibly to a 

 most interesting lack of diffei^entiation and specialisation 

 between the various constituents. The chromatin is not 

 marked off in the form of distinct chromosomes, nor are the 

 centrosomes — assuming my interpretation of the figures to be 

 correct — distinguishable as such. The three elements, chro- 

 matin, spindle, and centrosome, act in concert in the formation 

 of the first two daughter-nuclei, and it is difficult to say where 

 one begins and the other ends. I suggest, therefore, that 

 the evidence afforded by Metamera schubergi tends to 

 support Siedlecki's view, expressed in connection with his 

 workon Caryotropha (8), that "we have inaprotozoan cell 

 but a single and simple nuclear apparatus before 

 us," and not a binuclear arrangement. 



In conclusion, with reference to the apparent isogamy 

 shown by this gregarine, it will be noticed that we have 

 another apparent exception to what Leger (13) deems the 

 general rule in gregarines, i. e. anisogamy. In this connec- 

 tion the recent work of Brasil (4) and Hoffmann (10) on 

 Monocystis, which had previously been considered isoga- 

 mous, is interesting. The work of the latter emphasises the 

 futility of drawing conclusions from stained preparations. 



