4 If. I.. WIKAIAN 



sliaiplx' (IcIiiuMl object in llic nucleus. Figure 5, .t, ?/, shows it 

 beginning to b(^ I'ecognizable. Figures 6 and 7 show it well 

 develo})ecl. Its history and (kn^elopnient are the same in both 

 races. Figures 5 and 6 ai'e from white material and figure 7 

 from the negro. Figure 4 gives an idea of its variations in 

 form .ind size. Occasionally its constituents form two separate 

 bodies. A huge phismosome, P, is also present at this time 

 but it may be readil}^ distniguished from the chromatin nucleolus 

 both by its spherical form and the fact that it takes the acid 

 stain. The chromatin nucleolus is distinctly bivalent and the 

 components are unequal in size. 



Figures 8, 9 and 10 illustrate some of the principal changes 

 occurring in the prophase. In figure 8 the chromatin nucleolus 

 {x, y) is rather sharply defined while the remaining chromosomes 

 are ragged in outline and stain weakly. This section does not 

 include the entire nucleus, a small part of which lay in the ad- 

 jacent section. In some cases the distinctly bivalent character 

 of these chromosomes may be seen. A circle, straight and 

 twisted V's, and thick constricted rods may be seen. Includ- 

 ing the chromatin nucleus 12 bodies may be counted in this 

 section; although it is incomplete — the cut ends of some of the 

 chromosomes lying in the next section. 



Figure 9 shows the entire nucleus of a slightly later stage. 

 The chromosomes have become more dense and deeply staining. 

 Here again 12 bodies may be counted, as is also the case in figure 

 10 which is a still later stage. The dotted outline in this figure 

 represents the outline of nuclear membrane which is disappear- 

 ing. The problem of how the process of reduction has been 

 brought about will not be entered into at this time. 



From the facts discussed up to this point the following general 

 conclusions are indicated: 



1. The chromatin nucleolus of the rest stage in both the white 

 and black race is formed by the union of two unequal sperma- 

 togonia] chromosomes and maintains its identity throughout 

 the entire peiiod intervening between the telophase of the last 

 spermatogonia! division and the prophase of the primary 

 spermatocyte. 



