Spermatogenesis in spiders. 535 



the cell (Fig. 60). The division of the autosomes is not attended 

 by any irregularities; but as they draw apart, we find a small 

 chromosome lagging behind in the spindle (Fig. 61 p). This is the 

 planosome; and judging from such cells as are shown in the figures 

 it is inferred that it does not divide at this time. 



Among the spermatids we sometimes find a cell which shows two 

 nucleoli instead of the usual single form (Fig. 62). Evidently the 

 small body represents the planosome. 



The general behavior of the hétérochromosome elements may 

 be given in a diagrammatic way. Diagram II. 



Maevia vittata female. 



Wallace, in her work on Agalena naevia, failed to find the 

 accessory chromosome in the female of that species, although she 

 describes the dimorphism of the sperm for the males. As far as I 

 can determine from her description, she did not examine dividing 

 cells in the female but based her conclusions on the fact that nucleoli 

 were absent from the primary oocyte during the growth period. 

 The question of whether or not the female carries the accessory 

 chromosome elements is of such fundamental importance when we 

 come to discuss the dimorphism which the males of Maevia vittata 

 exhibit that a study of the oogenesis of this form was undertaken 

 in order to determine this point. Although a large number of females 

 were sectioned, no oogonial divisions were found, only primary oocytes 

 being shown by the material. During the growth period there are 

 large nucleoli in the primary oocytes, but this evidence is too un- 

 certain to be trusted. In order to determine the condition of the 

 female, dividing gland cells were examined and the conclusions given 

 here based on these. 



A large number of mitoses were carefully examined before any 

 definite conclusion could be reached, but the occurrence of such 

 chromosomes as are shown in the spindle of a gland cell, Fig. 63, de- 

 monstrates, I believe, the presence of two measures of accessory 

 chromosomes in the female. In the cell shown in Fig. 63, the auto- 

 somes have the usual V-shape, while lying to one side of the spindle 

 we find a quadripartite chromosome undergoing division. This body 

 is composed of four rod-like elements "^"; these divide and are 

 equally distributed to the two poles (Fig. 63). Only one possible 

 interpretation can be admitted here, and that is, that these rod-like 



