CHAPTER: II. 
BIONOMIC LAWS. 
I. Bronomic LAws AND THE METHOD OF THEIR INVESTIGATION. 
1. Bionomics and Its Scope. 
The organic world as we find it consists of many groups of individ- 
uals, each group, with but few exceptions, being propagated by the 
union of male and female elements produced by parents belonging to 
the same group;* while the elements of different groups are either 
incapable of fruitful union or in nature seldom have an opportunity 
for such union. Each group possesses characters of its own, distin- 
guishing it from all other groups; and these characters are inherited 
by each successive generation of the group, except in cases known as 
alternating generations, in which the persistence of character is re- 
vealed in a series of two or more generations that return to the 
original form. These persistent groups which are prevented from 
crossing by the incompatibility of their sexual elements or by some 
other form of segregation are usually called species; but when the 
difference of character is slight they are often called varieties; and 
when the differences are not easily recognized they are not even 
regarded as different varieties. Each persistent group differing more 
or less from every other group, and reproducing its own form without 
commingling with other forms, I call a type. 
The doctrine of evolution teaches that the vast multitude of organic 
types now inhabiting the world are the descendants of but few and 
perhaps of but one original type. Bionomics is the science that treats 
of the origin of organic types and of the relations in which they stand 
to each other and to the physical environment.{ In this volume some 
of the fundamental laws of bionomics will be considered. 
2. Why we Commence with the Method of Evolution without first proving 
the Fact of Evolution. 
It may be thought by some of my readers that before discussing the 
laws of evolution logical method would demand that I should consider 

* Examples of these exceptions are found in plants that propagate by shoots or 
bulbs without ever producing seed, such as banana; also in parthenogenetic 
plants and animals. 
¢ Prof. KE. Ray Lankester has proposed this use of the word “‘bionomics”’ in the 
article on Zodlogy, in Encyc. Brit., gth ed. 
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