MORPHOGENESIS OF THE MAMMALIAN OVARY 353 



phologieal differentiation obtained by this technique is particu- 

 larly serviceable. The dark blue interstitial cells and the epi- 

 thelial structures a lighter blue contrasting strikingly with the 

 golden brown of the stromal tissue and thus permitting them to 

 be readily distinguished without high power examination, while 

 at the same time a good fixation of cytoplasmic and nuclear de- 

 tail was obtained. • 



The study began with a fetus of 75 mm. total length, which cor- 

 responds closely with the forty-day fetus of Sainmont. At this 

 stage the morphology of the testis is fully established, as is also 

 the general morphology of the ovary, which consists of primitive 

 medulla and primitive cortex both composed of cordlike groups of 

 epithelial or epitheloid cells as the parenchyma, with strands of 

 stroma cells interspersed. The parenchyma of the primitive 

 cortex is in broad connection with the surface epithelium and 

 consists largely of genitoid cells with but few indifferent cells dis- 

 cernible. The strands of stroma cells are small and relatively 

 insignificant. The parenchyma of the primitive medulla is made 

 up-of genitoid cells and indifferent cells the latter present in much 

 greater amount as compared with the cortex. * The genitoid cells 

 resemble those of the primitive cortex markedly. While some of 

 them lie free in the stroma, the majority are surrounded by indif- 

 ferent cells, some few possessing an evident follicular epithelium. 

 Certain of these cells have taken on the character of 'egg cells.' 



The parenchyma of the primitive medulla and primitive cortex 

 are broadly confluent with each other, the separation of the two 

 being largel}^ indicated by a more marked accumulation of stromal 

 tissue in the intermediate zone, in the form of a trabecular mesh- 

 work of strands of spindle-shaped stroma cells, and blood vessels 

 which have a general longitudinal direction in this region. These 

 blood-vessels form convenient landmarks. The primitive cor- 

 tex (as well as the definitive cortex later) is strikingly free from 

 larger vessels. 



At the outset it may be said that it is obvious that in the mor- 

 phogenesis of such an organ as the ovary, its increase in size must 

 be kept constantly in mind, in the analysis. The ovary of the 

 75-mm. embryo or fetus in which the structural components — 



