No. I.] SPHYRANURA OSLERL 39 



over forty, and in the newly developed sphere are cylindrical in 

 shape and radiate from the centre to the periphery adjacent to 

 which the nuclei are placed. (Fig. 15,^.) When the nuclei 

 of these cells are round they do not measure more than 

 between 3 and 4 ^l. On the examination of many of these 

 spheres it is found that they present various stages of devel- 

 opment, the final outcome of which is the fully-developed 

 spermatozoids. This is represented in Fig. 15, c, dye, and f. 

 In c we have the initial stage with a small central cavity ; in d 

 the latter and the cell outlines have vanished, while the nuclei 

 are elongated ; in e this elongation of the nuclei is carried still 

 further, so that they now extend from the periphery to the 

 centre of the sphere. In all these stages the cytoplasmic ele- 

 ment of each cell degenerates more and more, till finally it 

 becomes fluid, and is probably partly absorbed in that condition 

 by the developing spermatozoid. In f we have briefly 

 represented the different stages of the development of the sper- 

 matozoid out of the round nucleus. Of great importance is 

 the arrangement and character of the chrom.atin in these ; at 

 first it is in the form of delicate looped fibrils which are inter- 

 woven with each other, but in the next stage these fibrils are 

 shorter ; then they take the form of excessively fine rodlets, the 

 axes of which are nearly parallel with the elongation of the 

 nucleus, while in the next stage again these become dissolved, and 

 now the elongated nucleus stains uniformly and homogeneously. 

 Finally, the outer or peripheral end of the elongated body 

 becomes pear-shaped, the remainder attenuates to a fine fibril, 

 which forms the tail of the spermatozoon, and the chromatin is 

 transferred to the pear-shaped head, which is the only part that 

 now stains with coloring reagents. The cytoplasma becomes, 

 as already stated, a fluid, and this, coupled with the fact that 

 there is no formed membrane proper to the original sphere, 

 easily permits of a rearrangement of the spermatozoids with 

 respect to one another. This rearrangement is a gradual one, 

 resulting in a sheaf of about \2 ^ in thickness, in which the 

 heads of the spermatozoids are all directed one way. 



In the cavity of a lobule also are irregular masses formed of 

 dividing cells. (Fig. 15, ^.) As the nuclei of these present 

 various sizes, intermediate between those of the parietal cells 

 (15 [i) and those of the fully formed spheres (4 \.l), the 



