44 
MR. E. EAT LANKESTER ON THE 
which are undoubtedly exceptional individuals of the migrated capsular cells which have 
not become fully metamorphosed. I have never observed more than fifteen of these in 
one egg, and those widely scattered, and all of those did not possess nuclei (Plate 12. 
fig. 25, also 24 & 26). They were observed only in Sepia, not in Loligo, and lying at 
a depth in the yelk, apparently in a zone of less dense yelk than that of the surface. 
Concerning these zones of yelk, or more strictly “ stratified shells ” (see Plate 11. fig. 12), 
there will be a few words to say below. 
Corpuscles like these nucleated corpuscles, but devoid of nucleus, and rounder or 
hexagonal in shape, were often observed by me in the eggs of Sepia during its post- 
seminary development, widely separate and quite accidental in mode of occurrence. It 
may be possible to attribute great significance to these enduring cells ; but the most 
satisfactory explanation of their occurrence seems to me that they are individuals which, 
owing to very slight individual differences of constitution (the existence of which may 
be assumed from the generality of the principle of variation), have delayed their vitelline 
metamorphosis, to which, however, they gradually (as evidenced by those without nuclei 
in older eggs) succumb. 
The process of proliferation from the surface of the ridges of the inner capsular 
membrane goes on pari passu with the dwindling of the ridges themselves, until at last 
there is no trace of the ridges left. The capsule then bursts at the pole opposite to 
that at which the peduncle is attached. The egg, with its surface free from all trace 
of the ridges, escapes, perfectly naked and devoid of any thing in the form of capsule, 
vitelline membrane, shell, or other envelope *. It falls into the wide membranous end of 
the oviduct, where, during the breeding-season, a number of free, naked eggs of this 
kind may be found. The mode of dehiscence I do not know in detail ; but, as in 
Plate 11. fig. 1, it is not unusual to observe ovaries with many empty shrunken capsules 
( c , c). 
Condition of the Capsule after escape of the JEgg. — The capsule, as thus left by the 
escape of the egg, consists of the outer capsular membrane, supported on its peduncle, of 
the main trunks of the blood-vessels which ramified between the inner and outer capsule, 
and of degenerating remains of some parts of the inner capsular membrane. These 
remains of the inner capsular membrane undergo a yellow degeneration, so as to form a 
true corpus luteum (Plate 11. fig. 21). The blood-vessels are easily traced on the inner 
surface of the empty capsules, and at intervals there are scattered shrunken yellow- 
coloured masses. Probably the whole capsule disappears before another breeding- 
season, but on this point I have no evidence. 
Condition of the Egg after escape from its Capsule. — The egg is now no longer 
“ ovarian,” but is still for a brief space of time prseseminary — that is, unimpregnated by 
the male element. 
* March 13th, 1875. — Evidence of a very delicate structureless chorion, adherent to the surface of the yelk, 
is obtained at a later period, when the superficial organs of the embryo are making their first appearance. It 
separates then in shreds. 
