I. On the structure of the immature ovarian ovum in the common fowl and in the rabbit. To which is appended some observations upon the mode of formation of the discus proligerus in the rabbit, and of the ovarial glands or 'egg-tubes' in the dog

Abstract

In the ovary of a laying hen, Graafian follicles are to be found in almost every stage of growth, and the fundamental parts germinal spot, germinal vesiole, yolk, and follicular epithelium exhibit differences both in relative size and in structure at various stages of growth. I will proceed to consider the structure of each fundamental part in detail, as it is presented in sections of the ovary prepared after hardening in picric acid and alcohol, and stained with logwood or with magenta. Germinal Spot .—In larger ovarian ova, those which are already ·5 minim, and upwards in diameter, the germinal spot appears homogeneous and stains of a uniform dark colour with logwood (fig. 1). It is either completely spherical in shape, or somewhat ovoid. In the latter case it is very commonly eccentric and placed close to the wall of the germinal vesicle, with which it may appear to be blended. When spherical it is often situated near the centre of the vesicle; and from its periphery, in what may be considered a typical condition, filaments of great tenuity radiate outwards to the wall of the vesicle, to the inner surface of which they are again attached, and that so closely that it frequently happens that when shrunken from the action of reagents, the filaments may break in the middle rather than suffer themselves to be dragged away from the wall (fig. 1, g ). These radiating filaments ramify and intercommunicate in such a way as to form a delicate network (intra-nuclear network) which as we have seen serves to connect the germinal spot with the inner wall of the germinal vesicle. The network is hardly at all stained by logwood thus presenting a marked contrast to the substance of the germinal spot; moreover the nodal points are not marked and the whole structure is comparatively indistinct. It is just such an appearance as can be produced in an albuminous fluid by coagulating reagents, and I am at present unable to decide clearly in my own mind, whether it is natural or has thus been formed artificially. In other ova, chiefly those of smaller size (figs. 2, 3, 4, and 8), the germinal spot is composed of two distinct substances, a homogeneous matrix ( ma. ) staining but slightly, and a number of coarse granules which are darkly stained by the logwood. The granules may be scattered equally thickly over the whole matrix, or they may leave a peripheral layer of the spot, clear, or again there may be a. clear part in the centre (fig. 3, c ) as well as at the periphery of the spot( 1 ). This last condition I have especially noticed in some of the smallest ova. As a rule the intra-nuclear network above described in the larger ova is not to be seen in the smallest ones. This may be accounted for by the assumption that the network is. formed subsequently by a protrusion of the homogeneous substance of the spot; i.e. , if we regard the network as a natural formation. On the other hypothesis, namely, that it is an artificial production, we must assume that there is less albuminous matter in the fluid which fills the germinal' vesicle of the smaller ovum, to what there is precipitated around the spot, and does not adhere together in the form of reticulating filaments, In almost all these smaller ova the germinal spot lies near the wall of the vesicle.