THE SPERMATOGENESIS OF THE MYRIAPODS. 



IV. — ON THE KARYOSPHERE AND NUCLEOLUS IN THE SPERMA- 

 TOCYTES OF SCOLOPENDRA SUBSPINIPES.* 



By Maulsby W. Blackmax. 



Presented by E. L. Mark. Received Juue 14, 1905. 



In making a comparative study of the spermatogenesis of different 

 species of chilopods the phenomena observed in Scolopendra subspinipes 

 are in some respects so markedly different from those already reported 

 as characteristic of S. heros (Blackman, :02 and :05) as to warrant 

 their treatment in a separate paper. The most striking differences are 

 dependent upon the fact that a large plasmosome, or true nucleolus, is 

 present within the nucleus of the spermatocytes of S. subspinipes during 

 stages of mitotic inactivity, while in the cells of S. heros no such struc- 

 ture is to be found. The presence of this body in S. subspinipes seems 

 to necessitate a corresponding variation in the behavior of the chromatin. 

 Although these differences are often quite marked, the process is essen- 

 tially similar in the two species. 



The material upon which this paper is based was collected by the 

 author near Flatts, Bermuda, during July, 1903. I am glad of this 

 opportunity of thanking Dr. E. L. Mark, director of the Bermuda Bio- 

 logical Station, for numerous courtesies extended to me while working 

 in the laboratory. 



The testes obtained from Scolopendra subspinipes are not so far ad- 

 vanced in development as those of S. heros, used in observations recorded 

 in my former papers (Blackman, .03 and :05). Very few sperma- 

 tozoa, spermatids, and secondary spermatocytes are to be found, nearly 

 the entire bulk of the testis consisting of growing spermatocytes and 

 cells in what I have elsewhere (:05) designated as the vesicle stage. 

 The proportion of cells of the smaller type does not seem to be as 

 great as that found in S. heros (Blackman, :01, :05) or in S. morsitans 

 (P. Bouin, :03). This may be, and probably is, due to the age of 



* Contributions from the Bermuda Biological Station for Research, No. 8. 



