O CALIFORNIA ACADEMY OF SCIENCES. 



grainy matter with a few more deeply staining micro- 

 somes. If this stage is previous to or later than the one 

 represented in fig. 2a, I am not able to say. 



After these stages are passed the spermatobium as- 

 sumes a broader shape, and at the same time the cyto- 

 plasm is seen to be differentiated. Clear, rounded, pel- 

 lucid sacs or vacuoles of different size begin to form 

 in the center of the cell, while at the surface below the 

 cytotheca are seen accumulating very small, extremely 

 regular, globular bodies. The former I term for the 

 present simply vacuoles, the latter cytospheres. The 

 vacuoles are first seen in the vicinity of the nucleus and 

 opposite to it (figs. 3« and 38^). Their contents do not 

 stain, but in some I could detect a faint shading in their 

 center. They are of different sizes; the largest appear 

 nearest the center, the smaller further away, or mixed 

 in with the other in an irregular manner (fig. 3«'). The 

 cytospheres are at first few and gradually increase in num- 

 ber. Correspondingly the vacuoles decrease in number 

 and size, and at last the protozoan cytoplasm contains 

 nothing but cytospheres of the same size and shape, the 

 vacuoles having disappeared entirely. If there exists any 

 connection between the vacuoles and the cytospheres I 

 cannot say. 



ADULT STAGE. FigS. 4, 5. 



The stage when all the vacuoles have disappeared and 

 the whole space outside the nucleus consists of cyto- 

 spheres, or at least is apparently filled with cytospheres, 

 may be termed the mature stage of this protozoan. 

 While the protozoan varies in size and shape in the same 

 host, the cytospheres appear to be alwa3^s of the same 

 size respectively in each species, at least from the begin- 

 ning of the adult stage to the forming of the spores. In 

 S^enuatobium edifidrili these cytospheres are several 

 times larger than in Spermatobium J^reuiidi. 



