Beniiet Mills Allen 99 



separated from the peritoneum (Plate III, Fig. 9). As we saw above, 

 this was foreshadowed in the 1.6 cm. stage l)y the transformation of 

 the basal nuclei of the sex cords into elongated connective tissue ele- 

 ments. They remain attached to the membrana propria, which in almost 

 all cases becomes ruptured and allows them to lie free between the 

 peritoneum and the intact inner portions of the sex cords. They now 

 form a connective tissue layer (albuginea) separating the sex cords from 

 the peritoneum. Here and there one can see a sex cord that still re- 

 mains attached to the peritoneum, and it is not at all difficult to find 

 portions of the membrana propria to which a number of the connective 

 tissue cells are still attached. The l^asement membrane shown in the 

 preceding stage to be forming at the places where these sex cords are 

 breaking away, has become completely formed except at a few points 

 where the sex cords are still attached. The connective tissue nuclei 

 formed in the manner above described are very similar to the mesenteric 

 nuclei. This fact has led many to claim that the albuginea is composed 

 of nuclei that immigrate from the mesenteric fundaments. We cannot 

 hold this view in the face of the facts above noted. Furtlier substantia- 

 tion of the view of development in sihi is furnished by the fact that 

 nuclei exactly like those forming the albuginea are found in the peri- 

 toneum, being no doubt formed by the same process that produced 

 the albuginea tissue. 



The two sexes cannot be clearly distinguished from one another 

 at this stage, the process above outlined taking place in both ovary 

 and testis. The separation of medullary cords is, however, not quite 

 so complete in the ovary as in the testis, yet this can hardly serve to 

 sharply distinguish the sexes at the stage now under consideration. 



The rete strands are quite well developed at this period, being long 

 and somewhat contorted (see Plate lY, Fig. 11), They usually take a 

 course more or less nearly parallel to the peritoneum to which they 

 still remain attached at their points of origin. In general, they grow 

 posteriorly, those found at the posterior end of the rete regions ex- 

 tending into the anterior part of the sex gland. Along their course 

 they frequently touch the capsules of Bo^vman, some of them growing 

 straight inward from the peritoneum in such a manner that their 

 tips come directly in contact with the IMalpighian corpuscles, thus ap- 

 pearing to form, in some cases, a part of their epithelial walls. This 

 closeness of union is frequently sufficient to deceive one into consid- 

 ering them to take their origin from the capsules of Bowman. 



At the boundary between sex gland and rete there is a transition 

 area in which the peritoneum becomes considerablv thickened. Pos- 



