34 
Evolution by Expansion. [January, 
descent. Thus an organism is expanded in the short period 
of gestation or incubation in precisely the same manner as 
its progenitors have been expanded through thousands of 
generations. 
What is the conclusion to be formed from these marvel- 
lous faCts ? That the organism is descended from an- 
cestors possessing the characters presented by the embryo ? 
Certainly this, and much more, — namely, that there indubi- 
tably exists in all organisms an innate power of expansion by 
which at least the individual is developed , for it is impossible that 
the egg (of a bird, for instance, during the period of incu- 
bation) can be aCted on by extraneous modifying influences ; 
and it is a fair and logical inference that the agent that pro- 
duced the metamorphoses in the development of the race is 
identical with the agent which produces precisely similar 
metamorphoses in the development of the individual. What 
can be more easy to conceive than that each individual may 
be expanded in an extremely slight degree beyond the stage 
of development of its parents ? 
What has been remarked with respeCt to the embry- 
onic development of the higher forms of life is equally 
applicable to the analogous phenomena of the metamorphoses 
of inseCts. The larval development is an expansion to a 
state of higher organisation, and takes place generally in 
the pupa, where no influence but an innate power can effeCt 
the changes. 
We may not be able to trace descent in the embryo beyond 
a certain point, and some stages are in many species sup- 
pressed that are exhibited by others. But, reasoning by 
analogy and by the evidence of geological records, we may 
conclude that the progenitors of all organisms must be 
among the earliest, and therefore lowest, forms of life. 
Thus it would appear that the simplest known forms of life 
are endowed, equally with the unformed embryo or seed, 
with a power of growth or expansion, a faculty of being 
drawn out through certain stages which occur always in the 
same order and with the same correlative features. The 
germs of each and every system that make up the entire 
structure, of a bird for instance, exist as certainly in the 
lancelet {Amphioxus , lowest of the vertebrata) as in the egg 
of the bird at the commencement of the period of incuba- 
tion ; they are, so to speak, latent in each case. In the first 
case, the development of those germs will occupy millions 
of ages ; in the second case, such age-development, having 
already been consummated, is recapitulated in the course of 
a few days. 
