BREEDING HABITS OF ALBINO RAT 



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with many more layers of cells. The egg nucleus presents a con- 

 stant appearance, a clearly defined nuclear membrane, scattered 

 chromatin and a deeply staining nucleolus. 



The second group includes those eggs which differ from those 

 of Group I only in their size and in the fact that they lie in 

 much larger follicles, the latter consisting of a large number of 

 cells closely packed but showing no radial arrangement except 

 in the layer immediately surrounding the egg. Such an egg is 

 shown in figure 7. 



The third group includes a much smaller number of eggs which 

 lie in follicles similar to the preceding, except that the cells lying 



Fig. 1 Normal resting follicle. X 630 



in or near the center of the follicle show a marked tendency to 

 separate, leaving a clear space. This condition may, however, 

 be found in follicles belonging to eggs of Group II, for the factors 

 governing the growth of the follicle are not, according to our 

 observation, constant, since growth may set in when the egg has 

 reached the stage of development included in either Groups II, 

 III or IV (figs. 2, 3 and 4). The nuclei of the eggs of this third 

 group show a marked change. The nuclear membrane is still 

 distinct, but the chromatin is less scattered and the nucleolus 

 has become partially vacuolated, since it shows much less affinity 

 for the stain. Figure 8 shows an egg of this group. 



The fourth group shows further modifications. It is at this 

 point that the maximum growth in the size of the follicle takes 



