1880.] 



in the common Fowl and in the Rabbit. 



243 



the other hand, are indistinguishable from those in the layer of granular 

 material which lies between the outer surface of the zona pellucida 

 and the innermost layer of cells of the discus proligerus (fig. 23, a). 

 There can be little doubt that this granular matter is produced by the 

 cells of the discus, and I cannot but conjecture with Waldeyer 

 that the granules in question pass bodily through the pores of the zona 

 to add themselves to the food material of the vitellus. I have seen no 

 appearances such as those represented by Pfliiger ( 12 ) and Lindgren 

 ( 13 ) of the passage of entire cells of the discus through the zona ( 14 ). 



Follicular Fpitheluim. — In the smallest Graafian follicles which are 

 met with in the ovary of the grown rabbit, the epithelium of the 

 follicle consists of a single layer of flattened cells, which tend, however, 

 to be thicker and more cubical on one side of the follicle, that, namely, 

 which is further from the surface of the ovary (fig. 25) ( 15 ). As the 

 ovum and follicle grow, the epithelium cells multiply and become 

 uniformly columnar, but long remain in a single layer (figs. 14, 15, 16, 

 18, 21). Presently another layer is formed within this first one 

 (fig. 17). This inner layer of the follicular epithelium {discus proli- 

 gerus) in the rabbit appears to be formed at the expense of the ovum. 

 At least, this is the only interpretation which I can adopt of the 

 remarkable appearances I am about to describe. 



Formation of the Discus Prcligerus in the Rabbit. — If we examine 

 those Graafian follicles in the rabbit's ovary whose follicular epithe- 

 lium is still composed of but a single layer of well-marked columnar 

 cells, it may frequently be observed that one or more nuclei are 

 imbedded in the peripheral layer of the vitellus (fig. 14, and this 

 part of the vitellus may be marked off from the rest by a sector 

 (fig. 16). The nuclei in question are oval, with their long diameter 

 parallel to the circumference of the ovum, and at right angles there- 

 fore to the long axis of the columnar cells and oval nuclei of the 

 follicular epithelium. The protoplasm in which they lie is more 

 sharply marked off from this epithelium than it is from the vitellus, 

 and, indeed, it looks like a part of the latter cut off, for it has the 

 same finely granular appearance, is stained similarly to that with 

 carmine and magenta, and is bounded externally by a direct continua- 

 tion of the general circumferential line of the ovum. Some ova are 

 met with which have only one of these nuclei, others, in which there 

 are two or more. When more than one, they may make their appear- 

 ance in different parts of the periphery, and these parts being 

 segmented off, the ovum, from being round may acquire a very 

 irregular shape (fig. 22). 



As before mentioned, the germinal vesicle is often bulged towards 

 that part of the periphery of the vitellus where the nuclei are 

 situated (fig. 18), and with care fine striatums may occasionally be 

 detected traversing the interval. Such appearances incline one to the 



