194 



MONTGOMERY — A STUDY OF THE CHROMOSOMES 



37. Milyas cinctua Fabr. 



In the single testis of this species studied (an individual of the month of September) 

 there were no mitoses. 



In the rest stage of the spermatocytes (Figs. 226-228) are found one long, rod- 

 shaped chromatin nucleolus and two or three smaller ones (TV. 2), all apposed to the true 

 nucleolus (JV). The long one is certainly bivalent, since it frequently shows a transverse 

 constriction (Fig. 228) or is bent at the middle point (Fig. 227); on account of the 

 length of each of its component parts it might be concluded that each of them is biva- 

 lent — i.e., thai, the whole clement is quadrivalent — but neither of the parts appear bipar- 

 tite, so that this long chromatin nucleolus would more probably be bivalent. In those 

 eases wbere oidy two smaller chromatin nucleoli are present (Fig. 228), each of them is 

 clearly transversely constricted (bipartite) and hence bivalent ; where three arc present 

 we find that one is bipartite and accordingly bivalent (Fig. 227), the other two are 

 spherical and hence univalent. By comparing Figs. 227 and 228 we find that the two 

 spherical chromatin nucleoli of the former would together represent one of the small 

 bivalent chromatin nucleoli of the latter. Thus we may conclude that there are three 

 bivalent, chromatin nucleoli present in these spermatocytes, though the two components 

 of one of them may Ik; separated. 



UMNOIIATII) lv 



38. Linmobates lineata Say. 



Of this small species I was able to procure the testes of only one (adult) individual. 

 The only stages of spermatogenesis present were spermatocytes in the growth period. 



In the large spermatocytes in the rest stage (I'l. V, Fig. 219) is found a large 

 chromatin nucleolus (JV. 2), usually apposed to the true nucleolus (N) in such a manner 

 that the chromatin nucleolus touches with one pole the nuclear membrane, with the other 

 the true nucleolus. 



II YDEOBATIDyK. 



39. Hygotrechus sp. 



Twelve testes were studied of this species (from the vicinity of Philadelphia). 



The relations of the chromatin nucleoli in the rest stage of the spermatogonia could 

 not be determined, since the nuclei are very small at this stage. 



The spermatogonia monaster shows on pole view (PI. V, Fig. 229) exactly twenty 

 chromatin elements, of which the eighteen largest are chromosomes and the two smallest 

 (JV. 2) probably chromatin nucleoli. 



In the synapsis stage of the spermatocyte (Fig. 230) are seen two small chromatin 



