536 P. W. WHITING 



The middles of the chromosomes are drawn together to the centre 

 of 69 a. The distal ends of each pair are united as shown in b. 

 Thus each united pair makes a complete ring by union of its 

 distal ends. One of these rings is seen in chromosome 2 of 69 b. 

 The lower focus of the middle (upper focus shown in a) forms 

 the right side and the upper focus of the united ends forms the 

 left side of this ring as shown in the illustration. Figure 69 c is 

 an optical cross section of the spindle fibers; 69 d is the upper 

 focus of the lower nucleus ; and 69 e its lower focus. The corre- 

 sponding chromosomes are again shown by the numbers. This 

 nucleus has been rotated so that its chromosomes are not at 

 right angles to those of the upper nucleus. The diffusion process 

 has progressed farther, so that the chromosomes are very thin. 

 They meet at the center of e, corresponding to the condition 

 seen at a. The more distal part of the chromosomes is at d, 

 and the sister monads of chromosome 3-3 * seem to be sepa- 

 rated. The distal ends of each are united, however, as in the 

 upper nucleus, so that in this case also each chromosome forms 

 a complete ring. 



♦A side view of this stage is shown in figure 70 and a little later 

 stage in 71. In figure 72 the daughter nuclei have become more 

 nearly round and a small granule is seen at the distal end of 

 each. The chromosomes are still heavily stained at the proxi- 

 mal ends. 



In succeeding stages, as shown in figures 73, 74, and 75, the 

 chromosomes become very diffuse, but do not entirely disappear. 

 The granule becomes more conspicuous and a second smaller 

 granule appears near it. These granules undoubtedly corre- 

 spond to the nucleoli of the spermatogonia and the first sper- 

 matocytes. They will be called the larger and the smaller 

 nucleoli. 



The spindle fibers of the first spermatocyte telophase are at 

 .first widely separated, (figs. 68, 69, and 70). They gradually 

 draw nearer together and appear very black. A constriction 

 may be seen at their middles so that they often look like a shock 

 of wheat (fig. 74). At a later stage they disappear. Black 

 bodies are seen at the time of the dissolution of the spindle fibers, 

 as shown in figures 73, 74, and 75. 



