differentiation of sex in the ovarian ova of the Rabbit. 611 
of a rabbit’s ovary. The discus proligerus cells are always attached 
to the zona during the growth of the ovum, it is in fact through 
them that nutriment is conveyed to the ovum. They are at first 
columnar, becoming more fusiform with the growth of the ovum ; 
as the latter attains maturity they are still further withdrawn 
until eventually, when maturation takes place, they are exceed- 
ingly attenuated, remaining attached to the zona only by fine 
processes which readily break away when the follicle ruptures, 
thus permitting the ovum to escape free from them. But in the 
healthy follicle these cells are always present either as columnar or 
fusiform cells, never as flattened cells. 
The so-called ripe “ male” ovum figured by Russo has nothing 
in common with this condition; it is, in fact, not a ripe ovum, it is 
an immature ovum lying in a cavity (in the discus) in a degenerate 
follicle, and I can only suppose he has jumped to the conclusion it 
is ripe because it possesses a nuclear spindle. But here again he 
is wholly mistaken ; a nuclear spindle, and polar bodies ajso, are 
commonly to be found in ovarian ova which, in consequence of 
degenerative changes, have lost connection with their discus cells ; 
such ova may even exhibit partial segmentation. Unless I am 
entirely mistaken such premature maturation phenomenon is 
associated with cessation in the supply of nutriment to the ovum, 
precisely as in the case of the healthy maturated ovum, with its 
polar bodies, where discus cells have been withdrawn by normal 
causes and the supply of nutriment thus curtailed or stopped 
entirely. 
It is astonishing that recognition of these facts should have 
escaped Russo, but it does not seem that he is familiar with 
various forms and degrees of degeneration commonly met with in 
the rabbit’s ovary. Certain of his figures of female ova are not 
free from suspicion of degenerate change though it is much less 
marked in them and is chiefly suggested by the condition of the 
zona. 
I find in my preparations that not infrequently the zona is 
absorbed, and when that is so the ovum loses connection with the 
discus cells and degenerates. In some of Russo’s figures I judge 
there is indication of the absorption of the zona, but it is 
important to note that unless the draughtsman was on the look 
out for this he might give the impression of degeneracy when 
perhaps it was not there ; the fact that these ova are still amply 
supplied with fat is evidence that degeneration, if it is in progress, 
has not gone far. 
It is impossible to avoid remarking that of all the ova which 
must have passed under his observation Russo figures only two 
which, so far as I can find, he directly refers to as “ male ” ova ; 
and it is significant that of these two, one is undoubtedly de- 
40 
VOL. XIV. PT. VI. 
