FREE BOOKS

Author's List




PREV.   NEXT  
|<   6   7   8   9   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25   >>  
different from men in important and constant particulars of their organization, we should rank them as members of the same Family, or of the same Genus, but as of distinct Species. That it is possible to arrange all the varied forms of animals into groups, having this sort of singular subordination one to the other, is a very remarkable circumstance; but, as Mr. Darwin remarks, this is a result which is quite to be expected, if the principles which he lays down be correct. Take the case of the races which are known to be produced by the operation of atavism and variability, and the conditions of existence which check and modify these tendencies. Take the case of the pigeons that I brought before you; there it was shown that they might be all classed as belonging to some one of five principal divisions, and that within these divisions other subordinate groups might be formed. The members of these groups are related to one another in just the same way as the genera of a family, and the groups themselves as the families of an order, or the orders of a class; while all have the same sort of structural relations with the wild rock-pigeon, as the members of any great natural group have with a real or imaginary typical form. Now, we know that all varieties of pigeons of every kind have arisen by a process of selective breeding from a common stock, the rock-pigeon; hence, you see, that if all species of animals have proceeded from some common stock, the general character of their structural relations, and of our systems of classification, which express those relations, would be just what we find them to be. In other words, the hypothetical cause is, so far, competent to produce effects similar to those of the real cause. Take, again, another set of very remarkable facts,--the existence of what are called rudimentary organs, organs for which we can find no obvious use, in the particular animal economy in which they are found, and yet which are there. Such are the splint-like bones in the leg of the horse, which I here show you, and which correspond with bones which belong to certain toes and fingers in the human hand and foot. In the horse you see they are quite rudimentary, and bear neither toes nor fingers; so that the horse has only one "finger" in his fore-foot and one "toe" in his hind foot. But it is a very curious thing that the animals closely allied to the horse show more toes than he; as the rhinoceros, for inst
PREV.   NEXT  
|<   6   7   8   9   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25   >>  



Top keywords:

groups

 

animals

 

relations

 
members
 

existence

 

organs

 

rudimentary

 
common
 

pigeons

 

remarkable


pigeon

 

fingers

 
structural
 

divisions

 

express

 
classification
 

systems

 

character

 

general

 

breeding


species
 

hypothetical

 
competent
 

effects

 

produce

 

proceeded

 

similar

 

allied

 
curious
 

finger


belong
 

rhinoceros

 

animal

 

obvious

 
called
 

economy

 

closely

 

correspond

 
selective
 

splint


result

 

expected

 

principles

 

remarks

 
Darwin
 

subordination

 

circumstance

 

atavism

 
variability
 

conditions