1878.] Considered from a Biological Point of View. 481 
or by rolling over. In many of the lower forms of animal 
life the sexes are not separated, the functions of the male 
and the female being exercised by one and the same indivi- 
dual. It is a fadt long familiar to the world that the polype 
may be cut into without injury, each part soon becoming a 
complete animal. 
To such simplicity of structure the completest contrast is 
afforded by the higher animals. Throughout their bodies we 
find a “ division of labour,” each function having its organ 
and each organ its distinct function. To trace how this 
differentiation is carried out would be wearisome, and, being 
admitted, is fortunately needless. 
It may be useful, however, to call to mind the facft that 
animals which when mature are broadly and easily distin- 
guished from each other, are more and more alike the earlier 
the stage of growth at which we institute a comparison. 
The differences between a baby chimpanzee and a human 
infant are much slighter than those between the adults of 
the respective species. If we extend our researches to the 
embryonic state we find that the rudimentary man can 
scarcely be distinguished from many of the other vertebrates. 
It is only, as Prof. Huxley points out, in the later stages of 
pre-natal growth that the human foetus differs from that of 
an ape. In the former the convolutions of the brain, ac- 
cording to Prof. Bischoff, reach about the same stage of 
development as in an adult baboon. The great toe, in man, 
is considered by Prof. Owen the most characteristic feature 
of the human skeleton ; but in an embryo about an inch in 
length Prof. Wyman found this member not lying parallel 
with the other toes, but projecting out from the side of the 
foot as it does permanently in the so-called Quadrumana in 
their mature condition. Thus plainly does it appear that 
differentiation is the way to perfection, each animal as it 
approaches maturity diverging more and more from other 
forms, from which in its earlier stages it was scarcely dis- 
tinguishable. 
Yet again, we may turn from a survey of the growth of 
the individual, and from a comparison of the highest and 
lowest forms of contemporary organic life, to the considera- 
tion of the successive phases of being that have peopled our 
earth. Here, too, we find the same great law prevail. In 
the remote past we find what are called “ generalised forms,” 
— animals which seem to have combined in themselves the 
rough outlines of what we now find developed into perfectly 
distinct beings. 
Suppose it were now proposed as an improvement in the 
VOL, VIII. (n.s.) 2 1 
