BLACKMAN. SPERMATOGENESIS OF THE MYRIAPODS. 341 



tudinally. In the spermatid it is for a time distinguishable from the other 

 chromosomes on account of its homogeneous condition. 



No traces of a nucleolus are to be seen at any stage after the late pro- 

 phase or early metaphase of the first spermatocyte. No such structure 

 reappears during the short prophase of the second spermatocyte, nor 

 have I observed it in the few spermatids to be found in my material. It 

 would seem that, in S. subspinipes at least, the nucleolus is present only 

 in stages of protracted mitotic inactivity. 



The principal facts of interest presented in this paper are due to the 

 presence of a true nucleolus or plasmosome in the nucleus of the sperm 

 cells during the so-called resting stages of mitosis. The presence of this 

 body seems to result in a considerable difference in the behavior of the 

 chromatin and in the structure of the karyosphere. Carnoy ('85) in his 

 " Cytodierese chez les arthropodes " has divided nucleolar bodies into four 

 classes, his conclusions being based in part upon observations on the 

 spermatogenesis of various Chilopods. These classes are as follows : 

 " (a) les nucleoles nucleiuiens ; sperules de nucleine amorphe, ou re- 

 massee en peleton serre ; (b) les nucleoles plasmatiques, masses albumi- 

 noides renfermant de la plastine ; (c) les nucleoles mixtes, qui sont 

 constitues par la reunion des deux especes precedentes en im corps 

 unique, oil chacune se maintient cependant sous une forme figuree ; 

 (d) les nucleoles noyaux, ou uoyaux en miniature, renfermant par con- 

 sequent tous les elements d'un noyau veritable : membrane, portion 

 plasmatique et portion nucleiuiene. 



In Lithobius, Scutigera, and Geophilus nucleoli of the fourth type, 

 nucleoles noyaux were found by Carnoy. These are similar in general 

 characteristics to the karyosphere in Scolopendra heros, although differ- 

 ing in many details. In Scolopendra dalmatica, however, according to 

 Carnoy ('85), "L'element nuclein d'ailleurs volumineux, est generale- 

 ment irregulier, bosseli, parfois moniliforme," and the nucleolus "n'est 

 pas un nucleole-noyau mais an nucleole plasmatique." The structure of 

 the nucleus " est done celle d'un noyau ordinaire." The nucleolus does 

 not stain with the chromatin stains and takes no part in the formation of 

 the chromosomes, which arise directly from the chromatic network of the 

 nucleus. 



In attempting to correlate these results of Carnoy with my own obser- 

 vations upon American species of the same genus, one of two conclusions 

 is necessary. Either Carnoy mistook the early prophase of the first 

 spermatocyte for the "resting stage," or the condition of the chromatin in 

 S. dalmatica presents yet another variation in its behavior from that 



