lO CALIFORNIA ACADEMY OF SCIENCES. 



of cytospheres in a spore showing the appearance of di- 

 vision (fig. 33«), the dark center remaining outside of 

 the four new microcytospheres. If the division goes still 

 further I am unable to state. It is not unlikely that it 

 does, as no such microcytospheres are seen in the young 

 protozoan. The cytospheres probably correspond with 

 the amyloid granules of Biitschli, and appear to be present 

 in most sporozoa. Besides the cytospheres and the vacu- 

 oles the cytosome contains, especially in the earlier stages, 

 a diffuse darker staining plasma (fig. 2«, etc.), which, 

 however, mostly disappears from view as the cytospheres 

 accumulate and increase in number. But little of this 

 plasma is seen in the fully developed form, and only rarely 

 is any found in the sporulation stage (fig. loa), and then 

 generally around the nucleus. 



NUCLEUS. 



A nucleus is nearly always present and well developed^ 

 though the chromatin bodies are not well definable. The 

 nucleus shows some very decided phases of development 

 and differentiation proceeding along two different lines, 

 accordingly as its division is caused by simple budding 

 and subsequent contraction, or by caryokinesis. The for- 

 mer phase is found in the early stages of sporulation, the 

 latter again in the last stages of this process. In the 

 resting nucleus we find especially prominent a single nu- 

 cleolus. In the adult stage the nucleus is furnished with 

 a distinct caryotheca. 



The nucleus is not always present in a fully developed 

 form and in some instances apparently absent, I think 

 this is due not to the total absence of the nucleus but 

 rather to the fact that it has disseminated itself all through 

 the elements of the cytosome or rather scattered its frag- 

 ment between the cytospheres, as I will endeavor to prove 

 directly. The nucleus when fully developed does always 



