BLACKMAX: THE SPERMATOGENESIS OF SCOLOPEXDRA. 59 



The cytoplasmic cleavage of the cell is accompanied by the same 

 phenomena as in the first spermatocyte. The midbody is poorly 

 developed and persists but a short time (Figs. 73, 74). Upon its 

 disappearance the cytoplasm takes on the dense stain which has been 

 noted as characteristic of the prophase of the first spermatocyte during 

 the formation of the astral systems. The archoplasm is again dissolved, 

 but is later converted into irregular reticulated masses, the presence of 

 which characterizes certain stages of the spermatid (Figs. 75, 76). 

 Meanwhile the centrosome, which has remained upon the cell mem- 

 brane since the completion of division, leaves this peripheral position 

 and comes to lie in one of these masses of archoplasm (Fig. 76). 



In the telophase the chromosomes go through the usual changes. 

 They have become granular and are now in the form of a number of 

 flaky masses of chromatin, arranged irregularly throughout the nuclear 

 space, which at this stage is surrounded by a delicate membrane. As 

 in the large type of cell, some of these spermatids possess the accessory 

 chromosome while in others it is lacking. After careful count it is 

 found that the cells possessing this element are about equal in number 

 to those in which it is lacking. This element has been divided in but 

 one of the preceding divisions, and during the other division has passed 

 over bodily into one of the resulting cells. 



6. The Metamorphosis of the Spermatids. 



In studying the metamorphosis of the spermatids of Scolopendra heros 

 most of the observations here recorded were made upon spermatids de- 

 rived from the larger spermatocytes. However, sufficient study of the 

 smaller cells was made to warrant the statement that the process is 

 nearly the same in both, and that the results of the transformation of 

 the smaller spermatids are spermatozoa identical with the larger ones in 

 all particulars except size. The behavior of the cells of the two sizes is 

 so similar, and the results are so nearly identical, that one is forced to the 

 conclusion that the spermatozoa of the two classes are equally functional 

 in the fertilization of eggs. This conclusion is also strengthened b} r the 

 similarity of behavior in all fundamental particulars of the spermatocyte 

 chromosomes of both sizes of cells. 



As a result of the two spermatocyte divisions, there are derived from 

 each primary spermatocyte four spermatids, two of which differ from the 

 other two in the possession of an extra chromatic element — the acces- 

 sory chromosome. In the telophase of the second spermatocyte this can 



