28 
Dr, Carpenter, on the Develoj)meiit of 
velopment of even the rudiment of ihe foot, I am satisfied that 
some further supply is a necessary condition ; and still more 
is needed for the development of the tentacula and eyes. It 
is very curious to see embryos that have attained this stage of 
evolution, entirely destitute of the means of developing any 
of the visceral apparatus ; this being formed at a later stage, 
and by the conversion of the large mass of conglomerate 
vitellus which has been introduced into the gastric cavity. 
And it is not less curious, that these abortive embryos should 
continue to live so long, being often observed swimming 
actively about, when the normal embryos have attained almost 
their full intra-capsular development. 
Although it is very common to meet with one or two of 
these abortive embryos among the twelve or twenty normal 
embryos, which are ordinarily contained within the capsule, — 
and although we may then attribute their abortion to some 
accidental interference with the process by which they should 
have attached themselves to the conglomerate mass, and have 
appropriated a part of its materials, — yet when, as sometimes 
happens, a large number of aborted embryos are found within 
one capsule, their abortion may be probably attributed to a 
deficiency in the store of food provided for them. Thus in 
one capsule I have found twelve nearly-mature, full-sized, and 
perfect embryos, twelve others decidedly under-sized, but still 
having all the organs complete which belonged to their period 
of development, and twelve embryos in various stages of 
abortion. The capsule contained no unappropriated yolk ; 
and the deficient size of some of the embryos, and the abortion 
of others, seem fairly attributable, therefore, to the inequality 
between the " supply " of nutriment, and the " demand " set 
up by so unusual a number of embryos. 
On the other hand it is not at all uncommon to find, in a 
capsule which contains an unusually-small number of em- 
bryos, a portion of the yolk-mass unappropriated, even when 
the embryos have nearly reached their full development. The 
embryos, when few in number, are commonly of unusually 
large dimensions ; thus in fig. 14 (Plate IV.) is shown such 
an embryo, gorged (as it were) with vitelline spherules, and 
having a residual mass of these, still unappropriated, remain- 
ing attached to its anterior extremity. 
I have not attempted to follow any part of the history of 
development into its details ; the whole of my time and atten- 
tion having been devoted to the solution of the one problem 
which I originally set myself to investigate ; and the limita- 
tion of my opportunity for observation having obliged me to 
