Bennet Mills Allen 97 



gal growth). Without doubt the sex cords are homodynamous with 

 • the rete tubules. 



Llf. cm. Embryo. — The nuclei of the peritoneum covering the rete 

 are more numerous than in the preceding stage, being even more 

 closely crowded. This has resulted in a further increase in the num- 

 ber of rete cords. Primitive ova may or may not occur in any given 

 rete cord (Plate II, Fig. 6), there being apparently no regularity in 

 this matter. 



Immediately ventral to the peritonemn of both rete and sex gland 

 there is a thickened area of stroma to which addition is constantly 

 being made by proliferation from the peritoneum. This thickening 

 is of no especial importance in the rete, but in the sex gland it, to- 

 gether with a similar but less important area dorsal to the sex gland, 

 furnishes the connective tissue that goes to form the mesentery. The 

 peritoneal nuclei of these mesenteric rudiments (Plate II, Fig. 7) are 

 cylindrical, with their long axes perpendicular to the long axis of the 

 sex gland. 



The rudiment of the sex gland shows very little advance over the 

 preceding stage in point of structure. There has been a continued 

 growth of the sex cords, "resulting in such a thickening of the sex 

 gland rudiment as to cause it to appear hemispherical in cross-sec- 

 tion (Text Fig. 2). As in the previous stage, the peripheral layer of 

 cells is not marked off from the underlying sex cords attached to it 

 because of the fact that it is still adding to the latter by rapid pro- 

 liferation. 



The capillary blood-vessels and stroma cells already noted are quite 

 evident in the interspaces between the sex cords. Here and there the 

 walls of these capillaries show spindle-shaped nuclei which are far 

 more attenuated than are the stroma cells. The latter are most 

 nmnerous at the distal (inner) ends of the sex cords where they form 

 a loose layer separated from the capsules of Bowman by a layer of 

 attenuated, deeply-staining connective tissue cells which have their 

 origin in the mesenteric fundaments already described. Posteriorly 

 the sex gland gradually shades off into the mesenteric ridge, the sex 

 cords becoming fainter and fainter and the primitive sex cells decreas- 

 ing in number. The last named are found to occur ahnost at the 

 posterior extremity of the mesonephros, where the genital ridge exists 

 only as a strip of tissue along which the peritoneum and underlying 

 stroma are thicker and denser than ordinary. There is an equally 

 gradual transition- from the sex gland to the rete. In following the 

 sex gland into the rete region, the first sign of transition from the 



