How Darwinism Stands To-Day 377 



4 



Origin of Variations 



Darwin had no theory of the origin of variations, and we 

 must join with him in saying "our ignorance of the laws of varia- 

 tion is profound." This is the central problem of evolution 

 the origin of the new. Yet certain possibilities have become 

 clearer since Darwin's day. When a white blackbird is hatched, 

 when an albino child is born, when a calf appears without horns 

 or a kitten without a tail, we interpret these variations as due 

 to the dropping out of the relevant hereditary item in the inher- 

 itance, and we know that in the history of the germ-cells there 

 are definite opportunities for such losses. 



When, on the other hand, an offspring has more than usual 

 of a certain character we can interpret this as due to its getting 

 a double dose from both sides of the house of the hereditary 

 item in question. If both parents are very dark and come of 

 very dark stocks, the offspring may be darker still, and the same 

 holds terribly true of a double dose of some disadvantageous char- 

 acter, such as deaf -mutism. The individual life always begins in 

 the fertilised egg-cell, and there may be accentuation of a charac- 

 ter, we say, if it is strongly represented both in the paternal and in 

 the maternal hereditary contributions. In the sperm-cell as in 

 the egg-cell there is a complete set of hereditary "factors" or 

 initiatives, and these two sets come into intimate and orderly 

 union in fertilisation. When the fertilised egg develops into an 

 embryo and into a young creature, there may be an expression 

 of some paternal peculiarities and some maternal peculiarities, 

 with a new pattern as the result. It must be understood that 

 although there is a complete assortment of hereditary qualities 

 in the egg-cell and also in the sperm-cell, it is usually only one 

 set that finds expression in the offspring in regard to any par- 

 ticular structure. The child may have its mother's hair, its 

 father's chin. In some cases a father's character as regards some 



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