112 bulletin: museum of comparative zoology. 



recent papers on this subject being the summary by Meves (:02 b ) and 

 the chapter on spermatogenesis in Korscheldt und Heider (:02). Instead, 

 I shall compare certain phenomena observed in Scolopendra heros with 

 those observed in other related animals. 



In a general way the development of the spermatid into the spermato- 

 zoon in Scolopendra shows phenomena similar to those observed by 

 Collin (:Ol), Tonniges (:02), and M. P. et Bourn (:03) in other genera 

 of myriapods. However, in man} 7 details it differs quite markedly from 

 the conditions observed by these authors. After a hasty study of the 

 process in several species of Lithobius, Geophilus, and Scutigera, I am 

 of opinion that this is not entirely due to differences of interpretation. 

 Nevertheless, it is my belief that there is greater uniformity than would 

 appear from the accounts hitherto published. This conclusion would 

 seem to be corroborated by the differences in results reached by Collin 

 and M. P. et Bouin working upon the same material prepared in the 

 same laboratory. In later studies upon the spermatogenesis of myria- 

 pods, I hope to return to this subject, and to attempt, at least, to cor- 

 relate the processes in different genera of chilopods. In view of the 

 considerable diffei'ences existing between the spermatocytes of two 

 species of Scolopendra (S. heros and S. subspinipes), and especially those 

 exhibited by the two classes of cells in the single species S. heros, 

 it would not be surprising if the cells of animals belonging to dif- 

 ferent families of myriapods should show considerable variation in their 

 development. 



A. " Nebenkern." 



One of the most interesting facts about the spermatids of myriapods 

 as the complete absence of a true Nebenkern, which has been shown to 

 be characteristic of certain stages in the transformations of the sperm 

 ■cells of insects. The word Nebenkern when used in the original sense, 

 Butschli ('71 a ), refers to that body in the spermatid which is produced, 

 ■at least partly, by the aggregation of the spindle remnants, and in later 

 stages gives rise to the inner tail envelope of the spermatozoon. In Scolo- 

 pendra, as we have seen, the spindle remnants are very often cast out of 

 the cell in the late telophase of the second spermatocyte, and are never 

 aggregated into a structure coinparable to the Nebenkern of insects. 

 The substance surrounding the centrosomes and the base of the axial 

 filament is not homologous with the Nebenkern, for, while it arises from 

 the archoplasm, its origin and behavior are quite different from that of 

 the Nebenkern in insects. In insects, according to the researches of 



