552 P. W. WHITING 



gonial metaphases and one prophase. By reason of the twist- 

 ing and the irregularity of the chromosomes at this stage 

 and because of the variable number of diffuse bodies of similar 

 appearance it has thus far been impossible to gain conclusive 

 evidence. If, however, as figures 12 and 14 seem to indicate, 

 we have a diffuse body attaching to one member only of one of 

 the large pairs, we have here a possible sex element and a con- 

 dition, comparable with that of Ascaris as shown by Herla ('95) 

 and Frolowa ('13). 



c. Nucleoli 



The plasmosome of Culex was noticed by Stevens ('09) and 

 was thought to absorb chromatin extruded by the spireme. 



Lomen ('14) noticed a clear space about the nucleolus and 

 concluded, therefore, that the spireme is not at all connected 

 with the latter. He considers that the variations in form of 

 the nucleolus are degenerative. He finds only one in second 

 spermatocytes, but occasionally two in the spermatids. 



I have nothing at all to offer as an explanation of the nucleolar 

 structures in Culex, but I believe that they all arise from a single 

 pair of chromosomes. In spermatogonia and first spermato- 

 cytes they never show more than four elements, two of which, 

 the terminal granules, are attached to the ends, and the other 

 two, the 'plasmatic' elements, are connected with the middles 

 of each member of one of the large pairs. Whether this is the 

 same pair that is associated with the 'sex-element,' I am unable 

 to say. The greater size of the plasmatic elements in relation 

 to the terminal granules, and the more precocious tendency of 

 the former to become diffuse, lead me to identify them with the 

 larger nucleolus of the interkinesis nucleus and of the spermatids, 

 while the terminal granules evidently form the smaller nucleolus 

 as shown in the figures. 



G. METAPHASE — STAGES A AND B 



The peculiar parallel arrangement of the pairs of chromo- 

 somes, as in stage B of the metaphase of Culex, has not been 

 noticed, so far as I am aware, in any other form. There are 



