92 The Rete-Cords and Sex-Cords of Chrysemys 
the anterior third of the genital ridge, whose middle portion is occupied 
by the sex-gland. As the rete-cords develop, they come in contact with 
slight evaginations from the Malpighian corpuscles in that part of the 
mesonephros which lies nearest the rete region. They then grow back 
to the anterior portion of the sex-gland and at a relatively late period 
of development advance along its entire length, giving off numerous 
branches (tubuli recti) which fuse with the tips of the seminiferous 
tubules. The rete-cords of the mammals are the peritoneal ingrowths of 
the anterior part of the genital ridge. Speaking in terms of phylogeny 
they are the sex-cords of the anterior part of the sex-gland. The anal- 
ogous structures of the turtle, the funnel-cords, appear at intervals along 
the entire lateral margin of the sex-gland. 
It is quite probable that the mammalian sex-gland was derived from 
that of some reptilian group and that some now existing groups of reptiles 
may show sex-gland conditions from which those of the mammals were 
derived. No existing group is more likely to show mammalian affinities 
than that of the Chelonia. 
Nothing exactly corresponding to the funnel-cord has ever been found 
in the embryonic development of the mammals. It is true that Aichel, 
oo, has found that the cortical portion of the adrenal body of the rabbit 
(Lepus) arises from funnel-hke invaginations of the peritoneum near 
the base of the mesentery. He is very positive in his claim that these 
are the peritoneal funnels of the mesonephros. Nevertheless, he does not 
claim to have followed these funnels back to stages in which they were 
actually connected with the Malpighian corpuscles. The rete-tubules that 
may have directly united the sex-gland proper along its entire length with 
the adjacent Malpighian corpuscles of the mesonephros have disappeared 
without leaving a recognized vestige, in any of the mammals thus far 
studied. The rete-region of these mammals has been evolved from that 
part of the genital ridge which was primitively the anterior part of the 
sex-gland in the ancestors of the mammals.’ 
It is scarcely possible to be more specific as regards the nature of the 
rete-region of the mammals. Two assumptions are possible: one, that 
1Tt will be well to note that in Chrysemys, several funnel-cords occur in 
a well-marked region, anterior to the sex-gland, in which the sex-cords remain 
vestigial. Upon closer study of some sagittal sections of the sex-gland and 
mesonephros of Chrysemys I have been struck with the resemblance that 
this region bears to the rete-region of the pig and rabbit as seen in similar 
sections. In Chrysemys the funnel-cords of this anterior region together with 
those of the sex-gland region are joined to form the central canal. This 
shows some points of resemblance to the portions of the rete-cords lying 
parallel to the peritoneum anterior to mammalian sex-gland. 
