600 THE STRUCTURE AND DEVELOPMENT 



reduced in quantity. Its cells retain precisely their previous 

 characters. 



The chief difference between the stage of five days and that 

 of two days after birth consists in the fact that during the 

 earlier stage comparatively few modified nuclei were present, 

 but the nuclei then presented the character of the nuclei of 

 primitive ova. 



I have ovaries both of the dog and cat of an equivalent stage, 

 and in both of these the cells of the nests or egg tubes may be 

 divided into two categories, destined respectively to become ova 

 and follicle cells. Nothing which has come under my notice 

 tends to shew that the tubuliferous tissue is in any way concerned 

 in supplying the latter form of cell. 



In a stage, seven days after birth, the same layers in the 

 germinal epithelium may be noticed as in the last described 

 stage. The outermost layer or pseudo-epithelium contains nu- 

 merous developing ova, for the most part with modified nuclei. 

 It is separated by a well marked layer of connective tissue from 

 the middle layer of the germinal epithelium. The outer part of 

 the middle layer contains more connective tissue and smaller 

 nests than in the earlier stage, and most of the cells of this layer 

 contain modified nuclei. In a few nests the protoplasm of the 

 developing ova forms a continuous mass, not divided into dis- 

 tinct cells, but in the majority of instances the outline of each 

 ovum can be distinctly traced. In addition to the cells destined 

 to become ova, there are present in these nests other cells, which 

 will clearly form the follicular epithelium. A typical nest from 

 the middle layer is represented on PL 26, fig. 39 A. 



The nests or masses of ova in the innermost layer are for the 

 most part still very large, but, in addition to the nests, a few 

 isolated ova, enclosed in follicles, are to be seen. 



A fairly typical nest, selected to shew the formation of the 

 follicle, is represented on PI. 26, fig. 39 B. 



The nest contains (i) fully formed permanent ova, com- 

 pletely or wholly enclosed in a follicle. (2) Smaller ova, not 

 enclosed in a follicle. (3) Smallish cells with modified nuclei of 

 doubtful destination. (4) Small cells obviously about to form 

 follicular epithelium. 



The inspection of a single such nest is to my mind a satis- 



