98 Z.O\0| PH YT Es: 
system cannot exist, but if muscular fibre be added, the nervous may 
receive its different degrees of developement. 
There is abundant reason, therefore, in their constitution, for the 
larger number of ovules in the inferior animals; for, from their 
nature, they can concentrate only a small amount of reproductive 
force on any centre; and, as the cellular tissue produces myriads of 
hairs, so animals of this composition may produce immense numbers 
of small ovules. Add muscular and nervous tissue, and the animal 
system may concentrate a much larger amount of force and nutriment, 
proceeding from a wider sphere of action. 
As the species among the inferior grades diminish in size, there is 
also a consequent decrease—the general constitution being the same 
—in the number of germs they produce; and, in the simple monad, 
we appear to have a single isolated sphere of reproduction, producing 
its single germ: the texture is mostly cellular tissue, and the size 
must be just that required to give vital force enough for a single 
germ; for when this animal enlarges, by nutriment received, so as to 
exceed its normal size, there is a tendency at once to form two 
centres; and, as enlargement goes on, subdivision actually takes 
place, and two animals are formed of the one. ‘The enlarged size 
produces more vital force than can belong to a single animal so con- 
stituted.* In larger animals, of similar constitution with the monad, 
the number of ovules produced is very large, for the reason, that the 
animal can concentrate on any single cellule only a small amount of 
vital force, and, as there is a large amount present, the germs must 
be numerous. As we ascend in the scale of being, the number of 
young diminishes. 
In the higher species, where a large nervous system is to result 
from the germinant cellule, the force required is greater than when 
this cellule is the germ of an inferior species, with an imperfect 
nervous system. ‘The physicat structure of the animal must there- 
fore be larger to produce the vital power needed for the elaborations 
that originate the germinant cellule of an animal of the higher 
grades. Size is, therefore, an important element in the system of 
organic life. 
96. Although the question is complicated by many circumstances 
* The relation between the number of germs and s?ze is still farther illustrated by the 
visceral lamellw in different species of Astrzeas, as exhibited in the closing paragraph 
of § 43 6. 
