292 NATHAN FASTEN. 



walled hollow tube, which stains lightly. The inner portion of 

 the central body is solid, stains intensely with nuclear dyes and 

 is embedded in the center of the nuclear-mitochondrial cup, im- 

 mediately below the wall of the first vesicle. Figs. 63-65 show 

 these structures nicely. Now the radial arms or rays of the 

 spermatozoon (Figs. 63 and 64, r) make their appearance. They 

 originate as outgrowths from the nuclear-mitochondrial cup, and 

 in the finished state they are stout structures with pointed ex- 

 tremities (Figs. 63 and 64, r). 



Soon the spermatids are completely transformed into mature 

 spermatozoa, and in this state (Figs. 65 and 66) they look like 

 ovoid, or spheroid structures, in which the radial rays are tightly 

 coiled around the nuclear-mitochondrial cup. Figs. 65 and 66 

 are drawings of mature spermatozoa as viewed, respectively, 

 from the side and bottom. An examination of these figures shows 

 the central body (6) located in the middle, and surrounding it in 

 order of sequence are the second vesicle ('), the first vesicle (v) 

 and the nuclear-mitochondrial cup (ti). In Fig. 65, the structure 

 of the central body (b) consisting of a hollow distal end and a 

 solid proximal end, can be distinctly observed. In this figure 

 may be also seen the densely staining chromatin-ring (d), located 

 at the upper end of the secondary vesicle. 



When the mature spermatozoa are studied in smear prepara- 

 tions which have been fixed with Bouin's fluid and stained by the 

 iron-haematoxylin and acid-fuschin methods, then the second 

 vesicle stains a dark amber color, while the primary vesicle takes 

 almost no stain and remains clear. In sections fixed with Flemm- 

 ing's fluid and stained similarly, the second vesicle remains more 

 or less transparent, while the first vesicle stains a dark brown. 



The mature spermatozoa are at first free, but when they make 

 their way into the vasa deferentia they are surrounded by the 

 membranous pouches or spermatophores already mentioned 

 under the discussion of the testis. Fig. 67 shows one of these 

 spermatophores when it is first removed from the vas deferens 

 of the living crab. Notice the numerous spermatozoa which are 

 compactly stored within its interior. 



