SPERMATOGENESIS IN THE ALBINO RAT 153 



arm which was characteristic of the accessory in the first sperma- 

 tocyte cells. This U might be interpreted as a V which had 

 failed to bring its arms together again. In that case it would be a 

 euchromosome. If that were the fact one would expect to find 

 more than one in a cell at times. No such observation has been 

 made, so that I am inclined to think it is the accessory and 

 maintains its diad condition in this form through interkinesis. 

 In the euchromosomes the chromatids seem to fuse very 

 closely. 



Interkinesis and second spermatocytes 



Interkinesis is well marked. ^ The daughter cells of the first 

 spermatocyte division reorganize into a complete nucleus and 

 characteristic cytoplasm, but without spireme formation appar- 

 ently. In form, the chromosomes, when they are differentiated, 

 resemble the spermatogonial chromosomes in prophase, but in 

 constitution they are very woolly. This condition is shown in 

 figure 25. Later the chromosomes shorten and thicken, the 

 delicate linin threads which have projected from their surfaces 

 lengthen and seem to form bridges between the chromosomes, as 

 seen in figure 26. The process of condensation continues, the 

 woolliness disappears, and the chromosomes group themselves 

 on the spindle as well-defined rods of various sizes. In the larger 

 ones curvature is to be seen. Figure 23 shows a lateral view of 

 three chromosomes and an end view of three others, all just 

 divided. The rod form is maintained in late anaphase, as shown 

 in figure 24 in the case of two chromosomes. The other chromo- 

 somes in the figure are also rod-shaped and of unequal lengths, as 

 revealed by focussing. The spindle fiber is attached terminally. 



In both figures 23 and 24 only part of the chromosomes present 

 are shown. Counts during any of these stages are difficult on 

 account of the close approximation of the chromosomes. There 

 is, however, no evidence of double reduction, the number of 

 clearly separate bodies being never less than 12 and often as high 

 as 15 in each stage, in addition to some w^hich are obscure. 



