SPERMATOGENESIS OF AMERICAN CRAYFISH 615 



(2) Type B', containing one chromatoid element (figs. 56 and 

 107). 



(3) Type C, without any chromatoid elements (fig. 45). 

 Type C is the most common of the forms produced. Roughly 



estimated, it is about four or five times as numerous as either of 

 the other two classes of spermatids produced. 



4-. Transforrnations of the spermatid to the syermatozoon 



'The transformations undergone by the spermatid to become 

 the spermatozoon are very interesting. The various types of 

 spermatids produced are small and contain minute, granular 

 nuclei which stain deeply with nuclear dyes. The cytoplasm 

 appears homogeneous throughout and stains but lightly. A 

 centrosome is usually found in it, and in types A' and B', the 

 chromatoid bodies are also visible in th^ cytoplasm. 



After the spermatid begins its transformation, however, the 

 chromatoid bodies cannot be followed. They evidently disinte- 

 grate and disappear. The nucleus is now observed to wander 

 to one pole of the cell (figs. 57-58, N). At the same time a 

 vacuole begins to form in the cytoplasm at the opposite pole 

 (fig. 57, T^. This vacuole increases in size and at the same 

 time the nucelus becomes more condensed into a crescent-shaped 

 plate (figs. 57-59, N). The centrosome is observed to migrate 

 between the nucleus and the vacuole, where it finally takes a 

 median position on the upper surface of the nucleus (figs. 57-60, 

 C). 



All these stages were also observed in living cells teased out 

 in Ringer's solution and stained with methylin blue or licht- 

 griin. In methylin blue the nucleus stains heavily and seems 

 to consist of granules and refractile droplets, thus giving them 

 the appearance of oil droplets. The cytoplasm is uniformly 

 granular and stains a very pale blue, while the vacuole is com- 

 posed of a liquid which refracts light strongly, but does not 

 seem to take the bluish stain readily. The centrosome stains 

 a deep blue. 



