THE ORGANIC CELL 
18 
The most recent research has placed this conclusion on an 
immovable foundation, and its absolute truth can be accepted 
unreservedly. 
The first stage in development is the division of the egg into 
two portions, each of which is a perfect cell in every respect. 
The two divide to form four, these again to form eight, sixteen, 
and so on, until at last the original cell or egg comes to be 
divided up into a host of cells, each one of which is as perfect 
as the original egg from which they all arose. It is from this 
mass of cells that the embryonic rudiment is built and, finally, 
the foetus, and then the full-grown individual. This splitting 
of the egg is called cleavage or segmentation. It must be 
remembered that cell-division does not begin with cleavage, 
but can be traced back into the foregoing generation, for it has 
been shown that the germ of the female and the sperm of the 
male arise by the division of cells pre-existing in the parent 
body. The germ and the sperm are therefore ‘ derived by 
direct descent from an egg-cell ’ or testis cell of the foregoing 
generation, and so on ad infinitum. 
Thus we arrive at the conception of an endless series of cell 
divisions extending far back to the very commencement of all 
life. The body must be looked upon as an excrescence growing 
out from this ‘ endless chain, whose end is but to die,’ the germ- 
cells, however, living on and on, ‘ carrying with them the tra- 
ditions of the race from which they sprang, and handing them 
on to their descendants.’ This is the modern standpoint of the 
problems of heredity and development. 
The whole teaching of evolution rests on two factors, viz. 
variation and heredity. Variation causes the appearance of 
new characters, and by heredity these are carried on to future 
generations. In the ‘ Origin of Species ’ Darwin accepted two 
modes of variation in formulating his doctrine : (1) Inborn 
variations, which appear at birth, without having in any way 
been affected by environment ; (2) Variations resulting from 
environment and produced during the individual life, e.g. the 
effects of use, disuse, &c. This second class of variation was 
accepted without hesitation by Lamarck, fifty years before 
Darwin, and is often spoken of as the Lamarckian factors. 
Around the question of the inheritance of the Lamarckian 
