Il6 J. F. MCCLENDON. 



when first formed are in groups of fours, as they elongate they 

 collect into larger groups. The cell boundary becomes granular 

 (Fig. 21) and the cytoplasm of adjacent spermatids fuses. Only 

 part of this cytoplasm goes into the formation of the spermatozoa 

 and the remainder forms a mass in the center of the group. 

 When the spermatozoon is fully formed no distinction can be 

 made between the cytoplasmic and nuclear parts of it in fixed 

 preparations (Fig. 22), but it appears as a homogeneous chromatic 

 thread tapering at each end. This spermatozoon is similar to 

 those of barnacles and some other Crustacea, and is non-motile in 

 sea water, though it is supposed, like other crustacean sperma- 

 tozoa to be stimulated to locomotion by the fluid in the ducts of 

 the receptaculum semenis. 



In some spermatids the chromatin collects into apparently 

 homogeneous masses close to the nuclear membrane, and the 

 nucleus grows at the expense of the cytoplasm (Fig. 23). This 

 process continues until the cytoplasm is represented by merely a 

 thin granular layer surrounding the distended nucleus (Fig. 24) 

 and finally disappears entirely (Fig. 25). The nuclear sap, which 

 is at first a thin fluid gradually becomes denser until it appears 

 homogeneous on fixation and takes plasma stains. The time at 

 which it acquires this power of taking stains is not sharply 

 marked off, as it appears gradually and as it is determined by the 

 duration of the staining and destaining process, but after all the 

 cytoplasm has disappeared the interior of the " nucleus " is easily 

 stained. Soon the nuclear membrane disappears and the chro- 

 ■ matin remains adhering to the surface of the sphere of material 

 that filled cavity of the nucleus (Fig. 26), and which was desig- 

 nated by the name nutritive-sphere in my former paper. The 

 spermatozoa are often arranged with one end against one of these 

 spheres, in a maramer similar to that in which the spermatozoa 

 of many animals are related to the nurse cells. 



When the products of the testes pass through the vasa defer- 

 entia and enter the spermatophores, the nutritive spheres form a 

 layer next to the wall of the spermatophore, and the chromatin, 

 which had separated as globules, forms a layer inside of the layer 

 of spheres. Lastly the spermatozoa arrange themselves more or 

 less radially, that is, with their ends abutting against the layer of 



