38 WRIGHT AND MACALLUM. [Vol. I. 



have a polygonal outline, while in transections they have an 

 elongated oval shape, the longest diameter being directed dorso- 

 ventrally (Fig. 14.) They are separated from each other by 

 fibrous tissue, which forms a basement-membrane to the cells 

 lining the lobules. 



Highly magnified, each lobule is seen to consist of a central 

 and a parietal part. The latter is formed of a single layer of 

 cells of uniform character and size, while the remaining con- 

 tents of the lobule are varied in structure, and present all the 

 stages of the development of spermatozoa. The parietal cells of 

 16 ^ in diameter form a continuous lining for the wall of 

 the lobule, and even extend into the cavity, and mingle 

 there with the other elements; their nuclei measure 12-15 ^ 

 and are surrounded by a sparing cytoplasma which does 

 not stain, while the nucleus itself stains deeply; and in sum- 

 mer specimens of Sphyranura is generally in one of the 

 stages of division. (Fig. 15,^.) The chromatin, when it is in 

 the skein form, is usually accompanied by a nucleolus of the 

 same nature, but not of the same staining capacity. These 

 cells we regard as the mother-cells of the spermatozoids. 

 There are in some series of sections a few cells, on the average 

 not more than half a dozen, which lie in the parietal layer of 

 cells, and are widely different from those just described. They 

 measure 16-20 ^, and their nuclei about 6 ^. The cells of 

 this class are somewhat irregular in form, have a feeble 

 staining capacity, the cytoplasma being formed of delicate, wavy 

 fibrils, the meshes of which contain a hyaline substance. The 

 nuclear cavity is filled with a clear homogeneous substance, in 

 which is a single nucleolus very feebly stained. These cells we 

 consider to be the persistent remnant of those out of which the 

 more abundant parietal cells have arisen. 



In the cavity of the lobule are, as already mentioned, all the 

 stages in the development of the spermatozoa. Of these the 

 one which always attracts attention at first is the sphere or ball 

 of cells (Fig. 14, Fig 15, <:, ^, ^) which is the result of the final 

 division of the cells of the lobule, and is usually termed a 

 spermatogemma. There may be as many as fifteen of these 

 spheres in a single lobule at one time, and the average diameter 

 of each is about 38 ^. The cells forming them number 



