20 
Dr. Carpenter, on the Development of 
necessary to its complete development ; while, on the other 
hand, it appears to us to be incontestable that it had never 
been in possession of the materials requisite for the formation 
of organs." 
Having had the opportunity, during a short sojourn at 
Tenby in August and September 1854, of applying myself to 
this investigation, I gladly availed myself of it ; for the pur- 
pose of affording to the statements and conclusions of MM. 
Koren and Danielssen, should I find them borne out by facts, 
that confirmatory testimony from an independent observer, 
which their aberrant nature seemed to require ; or, on the 
other hand, to correct them, if I should find them to be in 
error. I can honestly say that I entered upon the investiga- 
tion without prejudice of any kind ; for whilst, on the one 
hand, there appeared to be a strong antecedent improbability 
about their view of the case, yet, on the other, so many won- 
derful truths have been elicited by modern research,* — " so 
various^' (as my friend Mr. Huxley has well phrased it) " are 
the possibilities of nature," — that its very strangeness had 
almost something to recommend it. 
The general result of my observations is, that the process 
has been altogether misconceived by my predecessors ; that no 
such departure from the ordinary plan of development takes 
place, as the fusion of a number of originally distinct ova into 
a single embryo ; but that each embryo originates in a single 
ovum ; that it attains to a certain grade of development by the 
metamorphosis of the contents of its own vitellus ; but that its 
increase in size, and the continuance of its development, depend 
upon its appropriation, by a process of deglutition or swallow- 
ing, of a mass of additional or supplementary vitellus, the want 
or insufficiency of which occasions its partial or complete 
abortion. As to the immediate cause of the production of 
'monstrous' embryos, therefore,™ a phenomenon which I have 
found to be far more common than MM. Koren and 
Danielssen supposed, — I am in accordance with my predeces- 
sors, as I attribute it, with them, to the deficiency of nutritive 
material. But I differ from them essentially, not merely in 
regard to the mode in which this nutritive material is appro- 
priated ; but also in asserting that the production of embryos 
from single ova, instead of being an abnormal and occasional 
* What, for example, could have been more improbable, d priori, than 
the detachment of the arm of the male Argonaut, and its continued exist- 
ence as (in some sort) an independent self-moving being, so as to have 
been mistaken for a Worm, in order to serve as the instrument for the 
fecundation of the female ? 
