DAVIS: SPERMATOGENESIS. 105 



same rule holds here. Figures 88, 89 are drawn from two sections 

 of the same cell during the metaphase of the first division, all the chro- 

 mosomes being shown, while Figures 90, 91 are two successive sections 

 of another cell in the same stage and likewise show all the chromosomes. 

 In both cells the spindle fibers are e^'idently attached at the middle of 

 the arms of one of the larger autosomes, while in the case of the remain- 

 ing two large autosomes the attachment is nearer one end than the 

 other. 



In the first maturation di\ision, as we should expect, there are, in 

 addition to the three larger autosomes, five smaller autosomes in the 

 equatorial plate, which show approximately the same size relations 

 as the autosome pairs of the spermatogonia (Fig. NN, p. 96). 



As a consequence of the manner of attachment of the spindle fibers 

 described above, the first division must result in the separation of the 

 arms of the loop-shaped, bivalent autosomes. Although apparently 

 longitudinal in the case of the three larger autosomes, it is nevertheless 

 a true reducing di\'ision, since, as we have seen, each arm represents 

 a univalent autosome. As the univalent components separate they 

 assume the usual V-shape, but in the case of the three larger autosomes 

 the space between the arms of the Vs does not represent the longi- 

 tudinal split as in the smaller autosomes. As the V-shaped univalent 

 components of the larger autosomes separate (Fig. 93) each is clearly 

 double owing to the reappearance of the longitudinal split. Occa- 

 sionally one of the large autosomes may become so placed on the 

 spindle that the arms instead of lying on the spindle throughout their 

 entire length as usual, project away at an angle (Plate 7, Fig. 187). 

 In such cases it is the free ends of the arms which separate first, giving 

 rise to characteristic E-shaped forms (Fig. 188; Plate 6, Fig. 91). 

 Figure 94 shows the end of the anaphase of the first division. As in 

 the preceding species, there is in the secondary spermatocj^es a partial 

 resting stage (Fig. 95), which lasts but a short time. 



As the chromosomes become drawn into the equatorial plate of the 

 second dinsion figure (Fig. 96) the three larger autosomes form double 

 Vs and, as in the first division, the attachment of the spindle fibers is 

 near the middle of the V-shaped elements. Figures T and U show 

 that, as in the first di^'ision, in two of the large autosomes the spindle 

 fibers* are attached nearer one end than the other, while in the third 

 large autosome this attachment is at a point directly in the center. 

 Thus we have in each of these autosomes a characteristic method of 

 attachment to the spindle fibers, which persists through the spermato- 

 gonial and maturation divisions. During the second division the 



