42 
MR. E. RAY LANKESTER ON THE 
membrane. They lie perfectly naked within the egg-capsule. What Prof. Kollikek 
identified with the then metaphysically important vitelline membrane, is certainly our 
inner membrane of the capsule. 
It is the inner membrane of the capsule which, on the extension of long vascular 
trunks between it and the outer membrane, becomes longitudinally folded, in cor- 
respondence with those vascular trunks ; and now, as the growth of the egg rapidly 
advances, the growth of these inwardly projecting folds or double ridges goes on to an 
immense extent. The whole cavity of the egg-capsule becomes parcelled out by them 
(see Plate 11. figs. 7, 8, 9) ; they push into it from every side, and drive the germinal 
vesicle to an extreme polar position (fig. 8, gv ). Each fold is thoroughly supplied 
with blood-vessels, on which the rapid development of this great bulk of tissue, the 
increase in the total size of the egg, and the active secretion from the goblet cells of 
the whole of its inner surface depends. This folded inner capsular membrane, with 
its extensive system of vessels penetrating among its folds or follicles, may be regarded 
as a shut gland, constantly increasing in size and accumulating its secretion within its 
cavity. 
The blood-vessels which lie between the inner and outer capsular membranes have 
their own walls well marked, and in sections are not necessarily adherent either to one 
or the other. The main trunks are seen at their point of entrance from the peduncle 
in fig. 19, Plate 12, and the surface-network which connects the venous and arterial 
trunks at this pole. But besides vessels which may be seen thus on the surface, there 
are those which branch from them and penetrate between the pushed-in folds of the 
inner capsular membrane ; some of these ( hv ) are well seen in Plate 11. fig. 10, also fig. 9, 
and more minutely in Plate 12. fig. 23, in which the definite wall of the vessel, with 
its corpuscular elements, is distinguishable ; and it becomes obvious that there is nothing 
like a lacunar blood-space between the two membranes of the egg-capsule. The com- 
pleteness of this vascular supply, and the luxuriant growth of the inner capsular mem- 
brane, indicate great activity in this portion of the egg. The egg and its capsule 
attain nearly (Plate 11. fig. 8) if not quite full size, and still the septal ridges are every- 
where occupying its cavity. It is true that into the channels or follicles between the 
ridges the active pavement of muciparous cells has poured out a certain amount of 
material, and the egg has thus enormously increased in bulk. But there is so much 
space at present occupied by the ridges, that the egg itself cannot be said to have 
attained any thing like half its volume. 
Third Stage of Ovarian Growth . — This is effected by the gradual absorption of the 
entire inner capsular membrane, accompanied by the most active proliferation of its 
cells, which are thrown off in immense numbers to swell the yelk as the processes or 
ridges on all sides dwindle away and finally disappear. In figs. 10 and 11 sections of 
eggs are represented in this condition ; the folds of the inner capsular membrane, seen 
in section as processes formed by two rows of cells, with frequently a blood-vessel 
between them, are in course of degeneration ; and already a great mass has been added 
