THE GENERAL CONSTITUTION OF LIVING BEINGS. 95 
cult questions that we have enumerated above. In his 
view, the ordering and adjustment of the parts flow from 
the very fact of the gradual formation of those parts, and 
of the properties inherent in them. He shows how an ex- 
planation is to be found in the simultaneous operation of 
properties consubstantial with the elements, in the logical 
connection of generative, evolutionary, and nutritive acts, 
of all that had been heretofore attributed to the presence 
of a so-called vital principle. 
The hypothesis of a vital principle which codrdinates 
and rules the phenomena of life seems to contradict the 
fact, in this sense, that it is in the first place impossible 
to fix the exact moment at which this principle intervenes. 
We have the ovule—that is, a mere simple anatomical ele- 
ment, containing the vitellus. That ovule is already en- 
dowed with life while it is still dependent on the ovary. 
By an uninterrupted and inevitable chain of progress other 
anatomical elements unfold in it, in an ordained sequence, 
from the moment that it ceases to-be part of the ovary 
until the moment that the embryo is formed. This latter 
comes forth in the embryonic dot in the same way as the 
vitelline nucleus does in the vitellus. Each element, by 
the very fact of its existence and of the performance of the 
part peculiar to it, here becomes the condition of exist- 
ence of other elements necessarily appearing in the me- 
dium which it has engendered, and conducting themselves 
as it has done. Therefore, at what instant and in what 
way could a vital principle intervene in this series of en- 
genderings ? 
- It being known that the whole function of the vitellus 
is to present in succession those conditions required for the 
genesis of the different elements of the embryo, and that 
these are parts of one whole process, it is plain that, if one 
of the acts of development be hindered or modified, it will 
no longer go on in a regular manner. Experience entirely 
