SPERMATOGENESIS OF AMERICAN CRAYFISH 617 



view of a later stage, showing the vesicle (V) beginning its proc- 

 ess of invagination. The nucleus (A^) has now migrated to the 

 bottom of the cell and the strands of the centrosome (C) are seen 

 making their way through the cytoplasm (Z). 



The strands increase in length and, as they do so, the cytoplasm 

 spins out a thin arm along each one of them (figs. 65-66). At 

 the same time, the cytoplasmic cup with the nucleus in the bottom 

 decreases in width, thus being brought somewhat nearer to the 

 upper vesicle. This vesicle has also undergone considerable 

 change and now looks like a hemispherical cup whose mouth 

 • has become invaginated into the cavity (figs. 64, 65, 67-68, V). 



Figure 65 is a side view of the transforming spermatid. The 

 vesicle, V, is completely, formed, showing its invaginated edges. 

 The cytoplasm, Z, has produced the radiating arms along the 

 centrosomal strands, C. The nucleus, A^, forms the hq9,d piece, 

 opposite to the vesicle, V. Figure 66 is a top view of the same 

 stage showing all of the structures enumerated, except N, which 

 is completely hidden by the radiating arms. 



A recapitulation of the above description shows that the 

 spermatozoon now consists of: (1) A transparent upper vesicle 

 originating in the cytoplasm of the spermatid (figs. 57 and 65, V); 

 (2) Radiating arms, produced from the rest of the cytoplasm 

 (figs. 57 and 65, Z), and formed along the thin strands derived 

 from the centrosome (figs. 57 and 65, C); and (3) The compact 

 nuclear mass, situated in the bottom of the cytoplasmic cup 

 which is suspended from the upper vesicle (figs. 57 and 65, A^). 



In general, the genesis of the spermatozoa of the two species 

 of Cambarus studied are seen to be similar to the genesis of the 

 sperm of the other decapods as worked out by Labbe, Gilson, 

 Koltzoff, Retzius, Binford, Reinhardt and others. The central 

 body, however, the so-called 'tigelle' of the French investigators, 

 was not found in the species studied. 



Andrews ('04) worked on the spermatozoa of Cambarus 

 affinis and he asserts that "an examination of the stages of sper- 

 matogenesis in the crayfish leads to the provisional acceptance 

 of the view that the arms of the sperm are made from the nucleus 

 of the spermatid." My studies on Cambarus viriHs and C. 



