BY F. P. SANDES. 3(S9 



the tracing of the transition through a series of ovaries containing 

 corpora lutea in all stages of development? In Dasyurus, as 

 shown previously, the specialisation of the theca folliculi is rudi- 

 mentary; in other words, the accidental specialisation of the 

 theca folliculi seems to be practically omitted, possibly owing to 

 the lowly position of the animal in the mammalian order. There 

 is accordingly no similarity between the cells of the rudimentary 

 theca interna and the cells of the membrana granulosa or corpus 

 luteum in Dasyurus, and consequently there is no mistaking the 

 parts these two structures play in forming the corpus luteum. In 

 tracing the transition, of which His speaks, in fully formed 

 corporea lutea of Dasyurus, a certain apparent resemblance is at 

 times to be seen between some of the theca interna cells and the 

 cells of the corpus luteum. A superficial observer might view 

 some of the cells as showing a transition of the theca interna 

 cells into the cells of the corpus luteum, but if the growth of 

 that structure is traced through its various stages it is found 

 that the rudimentary theca interna plays no part in the forma- 

 tion of the characteristic cells of the corpus luteum, but limits 

 itself entirely to the giving off of vascular connective tissue 

 sprouts to the interior of the follicle. And this is what is to be 

 expected, for the theca folliculi, from the time of formation of 

 the primordial follicle up to the rupture of the follicle, merely 

 plays the part of a stratum of tissue whose function is to provide 

 blood supply and support to the contents of the follicle. And 

 indeed, the function of the theca folliculi seems to have been 

 neglected in this connection by the majority of authors. In 

 most animals there is described a thickening of the theca interna, 

 with lutein granules in its cells during ripening of the follicle, 

 which has been considered by some as a process of preparation 

 for the formation of the corpus luteum by that layer. In Dasy- 

 urus, on the contrary, there are no cells containing lutein granules, 

 and during the ripening of the follicle there is a progressive 

 diminution of the rudimentary theca interna and a rarefaction 

 of the theca generally, so that it is extremely unlikely that the 

 sudden rupture of the follicle should bring about such a change 



