168 ROBERT T. HANCE 



material excellent for checking the results obtained on the earlier 

 sectioned embryos. The clearness of the figures in these mem- 

 branes is evident from figures 81 to 85 and (photomicrographs) 

 89 to 93 and 95. 



Nearly all the cells studied were in prophase lending further 

 support to the idea of a 'cycle of division' (page 157). Twenty- 

 nine cells have been drawn and counted and the range of number 

 is the same as reported for the rest of the soma. The twenty- 

 nine cells fall into the following groups: 



Number of cases 10 2 4 1 3 3 2 1 1 1 1 29 



There are more cells in the forty class than found in the pre- 

 vious material but, as has been indicated, the frequency curve 

 of the first cells studied was without definite mode and it may 

 well be that the frequencies in this case are also governed by 

 chance. 



All that has been said on the structure of chromosomes on 

 page 163 applies to the chromosomes of the somatic cells as well 

 as those of the germ cells. 



The behavior of the ' extra ' chromosomes 



The chromosomes of the spermatogonia have been shown 

 to be constant in number, while those of the soma have a 

 rather wide range. Regardless of how this variation has come 

 about it is interesting to know how these 'extra' chromosomes 

 the chromosomes in excess of forty) behave. Aiq they carried 

 on as a part of the chromatic complex or are they thrown 

 out to degenerate in the cytoplasm? My evidence on this point 

 is not very concluwsive, as it is difficult to find anaphase stages 

 oriented in the proper plane and at just the right stage for count- 

 ing. In one case, however, I was able to make a fairly accurate 

 count of the chromosomes at one pole of an anaphase group. 

 In figure 57 the plate placed toward the upper side of the page 



