124 WILLIAM M. GOLDSMITH. 



upon a study of the development of this structure and its reaction 

 to stains. The earliest possible differentiation that can be ob- 

 served is found immediately following the synaptic stage (Figs. 

 5 and 6). The nucleolus at this time is of a more or less ir- 

 regular shape, and sometimes certain parts of it take the stain 

 less intensely. The more deeply staining areas give the appear- 

 ance of irregular granular masses. Although later development 

 shows that these masses are the sex-chromosomes in a diffused 

 condition, they are in this early stage poorly denned (Figs. 12 

 and 13). 



As the cell continues to grow, a gradual growth in the nucleolus 

 is likewise noted. The distinction between the chromatin and 

 the achromatin becomes more noticeable as the chromatin 

 aggregations gradually condense. The condensation of this 

 chromatin material causes certain areas of the nucleolus to 

 become clearer, or to take the plasma stain in case a counter 

 stain is used. Many instances are noted in which one end of 

 a chromatin body is much more compact than the other (Figs. 

 13 and 16), in which case the corresponding achromatic part of 

 the nucleolus is much more homogeneous. 



Another noteworthy feature, characteristic of these stages in 

 the early life of the nucleolus, is the irregular contour. In 

 practically every nucleolus the more granular and loose in 

 texture the chromatic areas are, the more irregular is the whole 

 body. For example, Fig. 14 shows various evaginations of the 

 plasma material in which are found chromatin-granules either 

 in a loose (d) or compact (a) condition. After the chromatin 

 granules are condensed into four compact bodies, the sex- 

 chromosomes, the whole mass presents a more globular appear- 

 ance (Figs. 17, 18, 19 and 20). Fig. 18 is a typical figure of this 

 stage. The condition shown in Fig. 17 is seldom observed, while 

 only three or four cells were found which show four clear-cut 

 chromosomes in the same plane (Fig. 20). There is nothing 

 problematical regarding this change to a uniform spherical shape, 

 as the withdrawal of the chromatin granules leaves the achro- 

 matic portion of the nucleolus less dense and thus gives it an 

 opportunity to assume a more globular form, in accordance with 

 the general laws of fluid action. In the previous stages the 



