Bennet Mills Allen 93 



the essential characters of the seminiferous tubules save for the fact 

 that they are by no means so well-developed nor so extensive as those 

 structures. (2) A zone of connective tissue separates the sex cords 

 from the peripheral peritoneal investment of the sex glands. It is 

 compact in the testis, while in the ovary it is loose, broad and irregular 

 in outline, forming only an incomplete barrier between the peritoneum 

 and medullary cords. In both ovary and testis this peripheral con- 

 nective tissue zone is continuous with masses of loose connective tissue 

 (stroma) packed in between the sex cords. I shall refer to it as the 

 albuginea in both testis and ovary, although that term is usually ap- 

 plied to it in the testis alone. (3) The peritoneal layer is thin in the 

 testis and its component cells are flattened. Quite a different condi- 

 tion prevails in the ovary where it is decidedly thickened and is seen to 

 be giving off cords of cells from its inner edge. These are the so-called 

 egg-tubes of Pfliiger. They are in some instances continuous with 

 the medullary cords, although such cases are rather rare, the two sets 

 of structures being usually distinctly separated by the albuginea. 



The posterior third of the genital ridge (mesenteric ridge) need not 

 be considered further save to note that it hecomes more elevated in 

 later stages and takes on a more decided mesenteric character. 



In the mesonephros there soon appear processes of degeneration 

 that "bring about decided changes. Even in the embryo 3.5 cm. in 

 length there is seen a commencement of degeneration in certain tubules 

 in its anterior portion. This process continues during succeeding stages, 

 chiefly affecting the Malpighian corpuscles, but sparing from 10 to 12 

 of the tubules destined to form the rete efferentia of the testis, but 

 which later degenerate in the female. To such an extent has this de- 

 generation process been carried on in the 10 cm. embryo that the por- 

 tion of the meso^iephros lying anterior to the hiluni is shrunken and 

 the investing peritoneum thrown into wrinkles. Degeneration of the 

 portion posterior to the hilum has just begun at this stage. In the 

 female, the shrinkage of the anterior part of the mesonephros has 

 caused the anterior ends of the Miillerian and Wolfiian ducts to be 

 bent over the ovary in a dorsal direction to such a degree that sec- 

 tions through this region show these ducts to be cut through twice 

 (Fig. 3). After this, the degeneration process rapidly reduces the meso- 

 nephros, until, in the 20 cm. embryo, it consists of little more than a 

 mere mass of connective tissue containmg a few scattered glomeruli 

 and uriniferous tubules, the vasa efferentia in the testis alone being 

 spared. 



