SPERMATOGENESIS OF THE BLACK-CLAWED CRAB. 279 



ends of the vas deferent ducts are surrounded by a single large 

 spermatophore. This is contrary to what has been found in the 

 other Brachyura studied, where numerous spermatophores are 

 developed. 



SPERMATOGENESIS. 



A. Spermatogonial Stages. 



In the black-clawed crab two distinct spermatogonial divisions 

 can be seen (Figs. 1-2 and 8-n). The primary spermatogonial 

 stages (Figs. 1-2) are considerably larger than those of the 

 secondary spermatogonia (Figs. 8 n) but otherwise the division 

 proceeds in the same manner as seen in Figs. 8-1 1 . The resting 

 primary spermatogonium (Fig. i) is almost twice the size of the 

 resting secondary spermatogonium (Fig. 8). Their structure, 

 however, is similar. Numerous chromatin clumps and linin 

 strands may be distinguished within the nucleus. A large 

 nucleolus may also be recognized. The cytoplasm is uniform 

 throughout, with the exception that occasionally larger masses 

 that stain somewhat like chromatin may be seen. These masses 

 are clearly discernible in Fig. I. The centrosome which is a 

 single granule is nearly always present. 



When any one of the spermatogonia divides, the chromatin 

 within the nucleus begins to fragment until a great many large, 

 heavily staining clumps appear, as shown in Fig. 2. The nuclear 

 wall soon breaks down with the result that the cell enters the 

 metaphase stage of division (Fig. 9). Polar views of the meta- 

 phase showed the chromosomes to be rather small and numerous. 

 Accurate counts could not be made although in many cases over 

 one hundred of them were found distributed throughout the 

 equatorial plane. But since it has been definitely determined 

 that there are 62 bivalent chromosomes in the reduced number, 

 there must be 124 univalent ones in the spermatogonial counts. 



The anaphase (Fig. 10) and telophase (Fig. n) stages follow 

 quickly, thereby completing the spermatogonial divisions. The 

 division of the secondary spermatogonia produces the resting 

 primary spermatocytes (Fig. 12) which then continue the matu- 

 ration process. 



In connection with the spermatogonial stages reference must 

 be made to the so-called "nutritive cells" (Figs. 3-7) which are 



