534 EMBRYOLOGY OF THE TURTLE. Part III. 
different from the chemical or physical properties of its constitutive elements. 
But what is that principle? It is the same something which distinguishes the 
parent, as an individual, from every other individual; for that immeasurably small 
egg grows to be another individual of the same kind, and never produces any 
thing else. It is the result of an organic impulse, acting as we see thought 
act in another sphere, when, in consequence of the utterance of a new view 
or a new truth, a new social organization is called into existence. As _ truly 
as the mind of man acts beyond the sphere of its organic functions when it 
pours forth its conceptions, so truly is the principle of life, characteristic of any 
parent being, transmitted to the egg when a new individual begins to grow. 
The comparison may be carried further. The results of the mental activity of 
one individual may be modified or stimulated by the action of other minds; as 
the progress of a new individual is modified by the different parts which the 
parents take in its formation. So the growth of the egg, begun prior to fecun- 
dation, is influenced by that act im a manner similar to the development of 
an idea which is modified by the influence of other ideas. We feel justified, 
therefore, in saying, that conception and fecundation must be, in a measure, intel- 
lectual acts, in however instinctive a way they may be accomplished. 
Sf CAV LOAN Var: 
FOLDINGS OF THE EMBRYONIC DISC. 
In a former section of this chapter,’ im which are investigated the changes 
through which the yolk of the fecundated egg passes, it has been shown, that 
the cells of which this body is composed undergo a series of transformations, end- 
ing with their embodiment in the embryonic disc, where each segment of the self 
dividing mesoblasts becomes individually a component part of the future cellular 
tissue. In a succeeding section,” the segmentation of the yolk was traced _ till 
this process terminated in shaping out a well-defined disc upon one side of the 
egg, though its further effects extend to a much greater area, if not all over 
the surface of the ege. 
We will now consider the development of the embryo from a different point 
of view. This well-defined disc, the so-called “embryonic disc,’ marks the place 
where the earliest and the most important organs of the animal originate. It is 
1 See Sect. 4, p. 616. 2 See Sect. 5, p. 523. 

