170 WALTER HEAPE. 
SuMMARY. 
The membranes surrounding the ripe ovarian ovum are two: 
(1) a single outer, thick, zona radiata, with a granular peripheral 
and a transparent inner portion, pierced radially by fine canals 
through which nutriment is obtained by the ovum from the 
follicular cells (of the discus proligerus) immediately in con- 
tact with the zona: (2) an inner very delicate vitelline mem- 
brane which closely covers the ovum itself; and between 
these membranes is a space, the circum-vitelline space. The 
confirmation of Reichert’s (No. 18), Meyer’s (No. 17), and 
van Beneden’s (No. 4) observations as to the presence of the 
inner delicate vitellime membrane appears of some interest as 
many embryologists are still sceptical of its existence, while the 
relation of the follicular cells with the radial canals of the 
zona supports the view as to the source of the nutriment of 
the ovarian ovum. On the other hand the fact that nothing 
was seen comparable to a micropyle in the zona, such as M. 
Barry (No. 3), and Meissner (No. 16), described, nor any 
follicular cells within the zona such as Lindgren (No. 15), 
von Sehlen (No. 21), and Virchow (No. 22), have observed, is 
some further proof that the conditions of the material investi- 
gated by these authors was abnormal. 
The yolk contained within the ovum, which is of two kinds: 
viz. (1) homogeneous vesicular bodies, (2) minute highly 
refractile granules, is contained within the meshes of a proto- 
plasmic reticulum ; it is dense and contains no large globules 
such as Beneden (Nos. 6 and 7) describesin theBat’sova. The 
rounded or oval nucleus contains a single centrally placed nu- 
cleolus and a variable number of smaller or larger granules, 
which may possibly be considered as nucleolar material. 
During maturation the vitellus becomes divided into a 
medullary granular, and a cortical non-granular portion, the 
circum-vitelline space between the zona radiata and the vitelline 
membrane is enlarged, while the vitellus itself contracts away 
from the vitellime membrane excepting (1) here and there 
where pseudopodia-like processes connect the two, and (2) at 
