REPRODUCTIVE ELEMENTS IN MYXINE GLUTINOSA. 59 



are blood-vessels. The connective-tissue layer passes off into 

 the thin flat raesoarium (me.). On the surfaces of the latter, 

 as well as on the outer surface of the follicle, there is doubtless 

 a thin flat epithelium, but this is so indistinctly differentiated 

 from the connective tissue that it does not show itself in 

 sections except by its nuclei. Within the connective-tissue 

 layer is the epithelium of the follicle (b). This epithelium is 

 composed of elongated cells disposed with their axes perpendi- 

 cular to the surface of the epithelium. There are several j 

 layers of these cells as shown in the figure, but the layers are 

 not regularly arranged, in some places three, in others four or 

 five nuclei succeeding one another in a radial direction. At 

 the exact pole of the egg there is a diff'erentiated portion of 

 epithelium, where a proliferation of the latter has taken place. 

 This portion is composed of polygonal cells which are little or 

 not at all elongated, and towards the egg it runs out into a 

 thin cylindrical process which penetrates the next layer, as 

 shown at e.p. The next layer (c) is thin and membranous. In 

 the living egg it is doubtless in contact with the epithelium, 

 and the separation between the two shown in the figure has 

 been produced by the action of the hardening reagents em- 

 ployed in the preparation of the egg. This layer as shown in 

 the figure appears under a low power single and homogeneous, 

 and it is in immediate contact with the substance of the ovum 

 proper, or, as it is sometimes called, the vitellus. The polar 

 portion of the vitellus which is in immediate contact with the 

 membrane (c) is granular in structure, stains well, and is proto- 

 plasmic in nature. In this protoplasmic cap is found the 

 germinal vesicle, shown in some of the other figures. Beneath 

 the membrane (c) at other parts of the ovum there is no separate 

 protoplasmic layer, the yolk-discs extending to the inner 

 surface of the membrane. The protoplasmic cap with its 

 germinal vesicle forms thus a germinal disc similar to that 

 found in the bird's ovum, and other meroblastic vertebrate 

 ova. The rest of the ovum is composed principally of yolk 

 elements, the elliptical vitelline discs show in the figure. The 

 nature of the membrane (c) must here be particularly consi- 



