GERM CELLS IN ASCARIS INCURVA 67 



some lying opposite the end of the longer X-element. This 

 interpretation is confirmed by an inspection of anaphase figures 

 which I described in the preliminary report (Goodrich '14) 

 as follows: 



Early anaphase figures of the first spermatocyte show most clearly 

 the unequal nature of the separation of the chromosome groups. Thir- 

 teen autosomes l}dng at or near the periphery of the plate divide equally, 

 thus forming two anaphase plates of thirteen chromosomes, typi- 

 cally arranged in a ring except that at a point of one daughter plate 

 a gap is observed, opposite which in the other plate is a fourteenth 

 chromosome (fig. 18, a and c). There remain eight chromosomes 

 lagging in the center of the spindle and arranged in a characteristic 

 plate consisting of six chromosomes of average size, the microsome 

 and a larger long chromosome, arranged in an approximately oval 

 or circular plate with the long chromosome projecting from the pe- 

 riphery (fig. 18, b). As the daughter plates separate, this peculiar 

 group tips, apparently as a unit, so that the long chromosome ap- 

 proaches the gap in the ring of thirteen autosomes. Eventually this 

 whole group passes to the center of the ring and thus the two daughter 

 cells (second spermatoc3^tes) receive respectively 14 and 21 chromo- 

 somes. Size relations and position facihtate the identification of the 

 homologous daughter chromosomes of the anaphase plates when 

 these are observed within a single section (fig. 18, a and c). Thus 

 the thirteen autosomes of either daughter ring may be readily identified, 

 and by elimination the fourteenth of one ring unmated in the other. 

 This fourteenth chromosome must therefore be considered as a Y- 

 chromosome mated bj' that member of the X-group, the long chromo- 

 some, which is first inserted into the gap of the one ring, correspond- 

 ing to the space occupied by the fourteenth chromosome of the other. 



From the foregoing it will be clear that the secondary 



spermatocyte divisions should be of two classes, one showing 21 chromo- 

 somes including the microsome, and other 14. Examination of numer- 

 ous metaphase plates. has proved this in the clearest manner to be the 

 case (figs. 19, 20). 



The details of the spindle formation in the unequal division 

 are described in a following section, page 79. 



B. The oogenesis 



1. The oogonid. No oogonial metaphase plates sufficiently 

 clear to be figured had been found when the preliminary note 

 was written but by further search plates have been discovered 

 similar to those of spermatogenesis which when considerably 

 extracted will show individual chromosomes. Figure 21 shows 



