BLACKMAN: THE SPERMATOGENESIS OF SCOLOPENDRA; 



even in the vesicle stage this element retains all of its ordinary charac- 

 teristics. In the metaphase it can be distinguished from the other 

 chromosomes both by its form and the different relation it bears to tlio 

 poles of the spindle, it being connected by the mantle fibres to only one 

 of these, while each of the other elements is connected with both poles. 

 In the spermatids, instead of persisting for a considerable time, as in the 

 Acrididae, it breaks down nearly as rapidly as the other chromosomes, 

 and in a short time becomes indistinguishable from them. . 



These variations, as I have said, are but unimportant modifications of 

 behavior, and do not represent such fundamental differences as seem to 

 exist between the "small chromosome" (Paulmier) or "chromatin nu- 

 cleolus " (Montgomery) in Hemiptera and the accessory chromosome in 

 Orthroptera. If the observations of Paulmier and Montgomery concern- 

 ing the origin of the bodies described by them are correct, it is indeed 

 doubtful whether they represent the same structure as the accessory 

 chromosome. The " chromosome x " of Protenor (Montgomery) would 

 seem more closely to approach this modified chromosome in origin and 

 later behavior. 



Since the above was handed in for publication a paper by Miss Wallace 

 (:05) has appeared, which contains still another hypothesis regarding 

 the significance of the accessory chromosome. As a result of the matura- 

 tion divisions of various spiders, the accessory chromosomes (two) pass to 

 but one of the four spermatids derived from one spermatocyte, and only 

 this favored spermatid completes the metamorphosis into a spermatozoon, 

 whereas the other three degenerate. From preparations of the testes of 

 Lycosa, collected in November, which I possess, I can say with certainty 

 that no such degeneration of the spermatids occurs in this genus at least. 

 In these preparations all stages of metamorphosis are represented, and 

 there can be no doubt that all develop into spermatozoa. 



C. Synapsis or Pseudo- Reduction. 



The term synapsis, introduced into cytological literature by Moore 

 ('95), was employed by him to cover the period after the completion 

 of the last spermatogone division during which the chromosomes are 

 reduced to one half the somatic number. "The transition from the first 

 into the second spermatogenetic period is completed in the cells during 

 the rest which follows the last division of the first. . . . The commei 

 ment of this metamorphosis is marked by an increasing fineness of the 

 reticulum in the nuclei. After a while the nuclear network again grows 



