194 MAULSBY W. BLACKMAN. 



stage. This is true both with regard to the history of the cell 

 and as regards the morphology of its various structural elements. 

 But from now on the behavior in Scolopendra differs very mark- 

 edly from that of corresponding cells in other animals. In other 

 arthropods at this stage growth is practically completed and the 

 maturation mitoses immediately ensue. In Scolopendra the sub- 

 sequent processes are very different. The growth period has 

 hardlv begun and the maturation divisions do not occur until 



* o 



considerably later (probably several w r eeks or. even months). In 

 insects the segmented spireme is considered one of the earlier 

 stages of the active prophase, while in chilopods a condition more 

 closely approaching a true rest stage than that occurring at any 

 other time in the history of the spermatocytes, intervenes between 

 this stage and the first maturation mitosis. 



During this intervening stage the history of the spermatocytes 

 parallels in nearly all respects that of the typical female germ 

 cell of a like generation, and the changes which take place result 

 in a structure which if isolated would certainly be mistaken for 

 an immature egg. 



As I have reported in a preliminary paper, this resemblance is 

 true not only of the cytoplasmic but of the nuclear elements as well. 

 As the cell continues in its growth the chromatin segments be- 

 come larger and more diffuse. They no longer retain the stains 

 with the persistency which has characterized them heretofore. 

 This is probably due entirely to the fact that the granules are 

 farther apart and not to a change in the chemical nature of the 

 chromatin. Gradually they break clown and their subtance is 

 accumulated about the accessory chromosome, thus seemingly 

 increasing the bulk of this element greatly (Fig. 7). This proc- 

 ess continues until finally all of the chromatin of the cell is 

 aggregated in one large intensely staining body situated periph- 

 erally in close contact with the nuclear membrane (Fig. 8). The 

 remainder of the nucleus is occupied by a beautiful regular re- 

 ticulum, the achromatic character of which is shown by the fact 

 that it stains even less densely than the cytoplasmic reticulum 

 immediately without the nucleus. 



In a preliminary paper upon Scolopendra spermatocytes I 

 stated that I believed this nucleolus-like body to be a homo- 



