104 Eml)rvonic Development of Ovary and Testis of Mammals 



mass which is finally set free in the cytoplasm by the rupture of the 

 nuclear wall. It now breaks up into irregular fragments which finally 

 become more or less rounded and eventually disappear. Here and 

 there one finds nuclei of the seminiferous tubules and cords of Pfliiger 

 which degenerate in the same manner. This process takes place very 

 extensively in later embryonic stages. 



In both sexes the rete cords along at least three-fourths of the 

 length of the rete region have become separated from the peritoneum 

 by a layer of stroma. It was impossible to determine whether this 

 process is analogous to the separation of the sex cords from the peri- 

 toneum covering the sex gland. 



Attention has already been called to the degeneration of certain 

 Malpighian corpuscles of the anterior end of the mesonephros in the 

 3 cm. stage. In the particular specimen' now under consideration 

 (4 cm. embiyo) this process has continued, affecting eight of the most 

 anterior corpuscles. The remaining ten or twelve corpuscles between 

 the degenerate ones and the hilum of the testis are, as a whole, quite 

 normal. Certain of the more peripheral of these intact Malpighian 

 corpuscles send out short evaginations that come in contact with cor- 

 responding processes from the mass of rete cords and fuse with them 

 (Plate V, Fig. 15). In this manner preparation is made for the estab- 

 lishment of a subsequent connection between the mesonephric tubules 

 and the rete cords. Connection is also no doubt established without 

 the aid of these evaginations in cases where the rete tubules press 

 tightly against the capsules of Bowman. The number of the above 

 described evaginations arising from each Malpighian corpuscle varies 

 decidedly. In many cases there are none at all; in others there are 

 as many as three. 



Smaller evaginations from the capsules of Bowman were found in 

 a 3 cm. embryo. 



5.7 cm. Embryo. Ovary. — One is struck by the very close resem- 

 blance between the medullary cords and the cords of Pfliiger. They 

 are practically identical, position alone serving to distinguish them. 

 The medullary cords (Plate III, Fig, 10) lie in the central axis of the 

 sex gland, separated by a zone of connective tissue from the cord^ 

 of Pfliiger which project inwards from the peritoneum. Both ele- 

 ments are in large part composed of primitive sex cells — in fact there 

 are but few small, deeply-staining nuclei which may be identified as 

 those of rudimentary granulosa cells. The latter have no well-defined 

 limits, being in every regard similar to the cells of the peritoneal layer 

 from which the cords of Pfliiger arise. 



