232 MICHAEL F. GUYER. 



polar view, they lay most commonly with their ends toward the 

 periphery of the equatorial plate and their plane of curvature at 

 right angles to the chief axis of the spindle, and frequently they 

 were relatively near together, being separated by only some two 

 to four small chromosomes. Sometimes, however, the two curved 

 elements lay at opposite sides of the spindle as in Fig. 86. Rarely 

 the position of the two bodies on the spindle was such that one 

 had its plane of curvature parallel to the long axis of the spindle. 



THE CHROMOSOMES OF THE FEMALE. 



Before continuing with the later phases of spermatogenesis it 

 will be well to consider the condition of the chromosomes in the 

 early germ and tissue cells of the female chick. Photos 4 to 7 

 and Figs. 100 to 117 show representative stages of the chromo- 

 somes in the primordial oogonial divisions and in the divisions 

 of somatic cells as seen in the nephridial tubules. The latter, 

 as in the male, were often the more favorable for study. The 

 divisions of the primordial oogonia, indeed, were considerably 

 more difficult to decipher than those of the spermatogonia 

 because for some reason, possibly correlated with the larger size 

 of the cell, the chromosomes were frequently longer and more 

 thread-like and consequently more likely to interlace and other- 

 wise alter in fixation. Although in the ten-day chick whole 

 nests of oogonia would be found in various stages of division 

 it was rare to find stages that one could make heads or tails of 

 when it came to studying individual chromosomes. It was 

 hopeless to try to do anything with the late prophase stages 

 because the chromosomes even up to entering the equatorial 

 plate remained decidedly elongated and nearly all of them showed 

 more or less curvature. However, not a few dividing oogonia 

 were found in such condition as to show that a single charac- 

 teristic element was commonly present. While several chromo- 

 somes in a given equatorial plate might show more or less curva- 

 ture, this special element, commonly larger than the others, was 

 usually discernible in such division figures as showed the chro- 

 mosomes in any condition beyond that of a confused mass. In 

 somatic cells, especially those of growing uriniferous tubules, 

 conditions were considerably better. The individual chromo- 



