328 



found nearer one pole than the other. On a single slide were found 

 one hundred and twenty monasters of the first spermatocyte, ninety 

 of which showed the two accessory chromosomes nearer one pole, as 

 shown in Figs. 3 and 4 when mantle fibres were clear they were traced 

 to one pole only, see Fig. 3. In twenty-nine monasters the accessory 

 chromosomes were not distinguishable, and in one there were two good 

 sized ones at each pole. 



Fig. 3. 



Fig. 4. 



Fig. 5. 



In studying the spermatogenesis of insects, Montgomery and Paul- 

 MiER have found that the accessory chromosome passes over undivided 

 into one of the daughter cells, in the second spermatocytic division, 

 and HiNKiNG describes a "nucleolus" behaving in the same way. In 

 the spider the position of the two chromosomes nearer one pole gives 

 the impression that this unequal distribution occurs in the first 

 spermatocytic division. One thing, however, opposes this interpretation 

 and that is that in the monaster of the second spermatocytic division 

 two elements are again found in eccentric position but of half the 

 size of those found in the preceding cell-division. The position nearer 

 one pole might mean merely delayed distribution but there is not yet 

 at hand sufficient data from which to draw a conclusion. 



In sections passing through the equatorial plate of the monaster 

 of the first spermatocytic division two well defined bodies are usually 

 found near the periphery of the cell (Fig. 5), and in position, sharpness 

 of outline and density these correspond with the two elements seen 

 in a lateral view of the monaster. (Figs. 1 — 5 semi-diagrammatic.) 



Marine Biological Laboratory, Wood's Holl, Mass., 

 July 14, 1900. 



Literature. 



1885. Caknoy, La cytodierese chez les Arthropodes. La Cellule, Vol. 1. 

 1890. Henking, Unters, über die ersten Entwickelungsvorgänge in den 

 Eiern der Insecten. Zeitschr. f. wiss. Zool., Bd. 51. 



