92 Heredity and Variation in Modern Lights 
If, then, progress was to be made in Genetics, work of a different 
kind was required. To learn the laws of Heredity and Variation 
there is no other way than that which Darwin himself followed, the 
direct examination of the phenomena. A beginning could be made 
by collecting fortuitous observations of this class, which have often 
thrown a suggestive light, but such evidence can be at best but 
superficial and some more penetrating instrument of research is 
required. This can only be provided by actual experiments in 
breeding. 
The truth of these general considerations was becoming gradually 
clear to many of us when in 1900 Mendel’s work was rediscovered. 
Segregation, a phenomenon of the utmost novelty, was thus revealed. 
From that moment not only in the problem of the origin of species, 
but in all the great problems of biology a new era began. So un- 
expected was the discovery that many naturalists were convinced it 
was untrue, and at once proclaimed Mendel’s conclusions as either 
altogether mistaken, or if true, of very limited application. Many 
fantastic notions about the workings of Heredity had been asserted 
as general principles before: this was probably only another fancy of 
the same class. 
Nevertheless those who had a preliminary acquaintance with the 
facts of Variation were not wholly unprepared for some such revela- 
tion. The essential deduction from the discovery of segregation was 
that the characters of living things are dependent on the presence of 
definite elements or factors, which are treated as units in the pro- 
cesses of Heredity. These factors can thus be recombined in various 
ways. They act sometimes separately, and sometimes they interact 
in conjunction with each other, producing their various effects. All 
this indicates a definiteness and specific order in heredity, and there- 
fore in variation. This order cannot by the nature of the case be 
dependent on Natural Selection for its existence, but must be a con- 
sequence of the fundamental chemical and physical nature of living 
things. The study of Variation had from the first shown that an 
orderliness of this kind was present. The bodies and the properties 
of living things are cosmic, not chaotic. No matter how low in the 
scale we go, never do we find the slightest hint of a diminution in 
that all-pervading orderliness, nor can we conceive an organism 
existing for a moment in any other state. Moreover not only does 
this order prevail in normal forms, but again and again it is to be 
seen in newly-sprung varieties, which by general consent cannot have 
been subjected to a prolonged Selection. The discovery of Mendelian 
elements admirably coincided with and at once gave a rationale of 
these facts. Genetic Variation is then primarily the consequence of 
additions to, or omissions from, the stock of elements which the 
