x PHENOMENA OF ORGANIC NATURE 319 
; in weight, undergoes a series of changes,— 
wonderful, complex changes. Finally, upon its 
surface there is fashioned a little elevation, which 
afterwards becomes divided and marked by a 
ve. The lateral boundaries of the groove 
extend upwards and downwards, and at length 
give rise to a double tube. In the upper and 
smaller tube the spinal marrow and brain are 
fashioned ; in the lower, the alimentary canal and 
heart ; and at length two pairs of buds shoot out at 
the sides of the body, and they are the rudiments 
of the limbs. In fact a true drawing of a section 
of the embryo in this state would in all essential 
tespects resemble that diagram of a horse reduced 
© its simplest expression, which I first placed 
before you (Fig. 1). 
_ Slowly and gradually these changes take place. 
The whole of the body, at first, can be broken up 
to “cells,’ which become in one place meta- 
morphosed into muscle,—in another place into 
gristle and bone,—in another place into fibrous 
issue,—and in another into hair; every. part 
ecoming gradually and slowly Salita aad as if 
vere were an artificer at work in each of these 
Beenie: structures that I have mentioned. This 
bryo, as it is called, then passes into other con- 
at I should tell you that there is a time when 
a embryos of neither dog, nor horse, nor porpoise, 
lor monkey, nor man, can be distinguished by any 
ental feature one from the other; there is a 
