348 H. S. DAVIS 



acetone so that in strongly decolorized preparations they can 

 scarcely be distinguished. Moreover, the vegetative nuclei 

 are never surrounded by a specially differentiated area of cyto- 

 plasm as are the generative. The number of vegetative nuclei 

 varies greatly, the older trophozoites containing more than the 

 younger, although there are probably never less than four. Usu- 

 ally they are confined to the larger, attached end of the troph- 

 ozoite where the cytoplasm stains more deeply and is evidently 

 much denser than in other parts of the body. 



The generative nuclei, although varying considerably in size, 

 are always much smaller than the vegetative and have a very 

 different appearance. They may occur singly or in groups and, 

 like the generative nuclei of the disporous form, are surrounded 

 by a specially differentiated area of cytoplasm forming a dis- 

 tinct cell (figs. 66 and 67). The chromatin is scattered in irregu- 

 lar clumps through the nucleus and there is usually no nucleolus. 

 The generative cells divide mitotically and in a large trophozoite 

 there may be a number of these cells present in the endoplasm. 

 They all have a similar structure but may develop into two 

 different types of reproductive bodies. 



Occasionally a degenerative cell is seen, in which division of 

 the nucleus is not followed by a corresponding division of the 

 cytoplasm. Successive nuclear divisions follow in rapid suc- 

 cession until eight nuclei are formed, all enclosed in a common 

 cytoplasmic mass (figs. 67 to 71). Meanwhile, the entire struc- 

 ture increases considerably in size, forming a very characteristic 

 rounded body, sharply marked off from the surrounding endo- 

 plasm (figs. 59, 60, 69 and 70). These bodies are probably 

 homologous with the pansporoblasts but have a very different 

 history from the ordinary structures of that name. They are, 

 in reality, similar to the gemmules formed by many species of 

 Protozoa. 



The gemmules at this stage have eight similar nuclei which 

 are closely crowded together, at the center. Surrounding them 

 is a layer of cytoplasm which is more finely granular and stains 

 more deeply than the undifferentiated endoplasm in which 

 they are imbedded. Often, as in figures 69 and 70, a clear 



