OVARIAN OVUM OF MARSUPIAI.IA AND MONOTREMATA. 119 



and leaving it for a long time in melted paraffin. In this way 

 it was possible to retain the entire contents of the follicles in 

 situ. Borax carmine was chiefly used as the staining reagent. 

 Fig, 1 gives a general view of ail the structures seen under a 

 low power in a complete section. The germinal epithelium is, 

 as usual, a single layer of the very low columnar type. It is 

 much lower than the cells lining the adjacent oviduct. The ar- 

 rangement of the stroma in the thin " albugiuea" seems to vary 

 in difl'erent parts of the periphery of the organ, sometimes one 

 layer being present, sometimes two or more, of which the cells 

 cross one another. An irregular layer of small follicles (cor- 

 tical layer of Schron) is next met with, and there is a special 

 tendency towards the formation of groups. Below this the 

 follicles increase in size, but the largest project from the sur- 

 face. In the centre of the organ there is a very richly -supplied 

 *' zona vasculosa,^' the vessels of which radiate outwards to the 

 large follicles. In the rapid growth of a large follicle, some of 

 the adjacent small ones are subject to such pressure that they 

 become drawn out at right angles to the force, and parallel 

 with the circumference of the large follicle (see fig. 4, e.f.). 

 Some of the follicles distorted in this way are found consider- 

 ably advanced in development, with the membrana granulosa 

 many cells deep. I have no doubt that this explains many of 

 the abnormally-shaped follicles described in the ovaries of 

 higher mammals j it is certainly the explanation here. 



The substance of the organ consists of a mixture of normal 

 stroma cells aud fibrous connective tissue. In the " tunica 

 fibrosa " of the largest follicles the peripheral layers consist of 

 fibrous connective tissue, the central of concentrically-arranged 

 stroma cells, with abundant capillaries just outside the mem- 

 brana granulosa (see fig. 6, f.t.). Yellowish granular cells, 

 united into lobes and cords, are very abundant in the zona 

 vasculosa (fig. 1), and isolated masses are also common, peri- 

 pherally (fig. 4, g.c). They are, doubtless, the traces of the 

 Wolffian Body, which have been described in other mammals. 

 There is no essential difference between the Marsupial ovary 

 and that of higher mammals in any of the points described 



