The stage of about the greatest development of both the vitelline membrane and zona radiata is represented on Pl.
The only membrane enclosing the individual eggs is the vitelline membrane.
Both the vitelline membrane and the zona radiata are found in Raja, but in a much less developed condition than in Scyllium.
vitelline membrane: the delicate tissue surrounding the yolk of an egg.
The big cells have now become flask-shaped like those in Scyllium, and send a process down to the vitelline membrane.
The zona is the first to disappear, and the vitelline membrane next becomes gradually thinner.
The ova of Gasteropods are exceptional in the fact that a vitelline membrane is rarely or never developed around them.
It is in many cases doubtful whether a particular membrane is a chorion or a vitelline membrane.
Each egg is encased in a vitelline membrane, but individual outer envelopes are lacking.
The membrane which invests the ovum of many of the Cœlenterata is probably a vitelline membrane.
vitelline membrane n.
The membrane enveloping the yolk of an egg. Also called ovular membrane, yolk membrane.
The pellucid zone of a mammalian ovum. Also called yolk membrane.