EVOLUTION OF ANIMALS AND PLANTS 573 







chromatin of the fertilized egg-cell in all animals and plants, 

 it follows that the new individual inherits from the two 

 parents. However, there may be a more striking resem- 

 blance to one parent. For example, the offspring of a pair 

 of pigs of which one is white and one black are often some 

 white, some black, and some spotted black and white. But 

 the white and the black ones have also inherited from each 

 parent, although in color they show relationship to only one 

 parent. It often happens that a pig which in color resembles 

 one parent will, in shape of head and body, or other char- 

 acteristics resemble the other. 



503. Law and Order in Biology. One who has never 

 studied biology might look upon a vast museum of natu- 

 ral history as a chaotic mass of specimens; but biologic 

 science has reduced them to order. There are many hun- 

 dred thousand kinds or species of living things wiiich can 

 be distinguished from one another; but after all, they are 

 remarkably similar, for they are dependent upon the same 

 fundamental substance, protoplasm, which must perforce 

 carry on the same essential life-processes in all plants and 

 animals. 



And what we find in biology is true in every other natural 

 science. Everywhere in nature there is law and order. 

 Planets and comets move in definite orbits, light and heat 

 and electricity are subject to unchanging laws, elements 

 unite and separate according to fixed principles in short, 

 all things in nature are conducted in accordance with law. 



It has been one aim of this book to make the reader realize 

 that the whole organic world, the field of biology, is subject 

 to definite laws to which the human species is by no 

 means an exception. Man is certainly an integral part of 

 organic nature, and it behooves him to study and apply 

 the discovered laws of biology upon which the continued 

 advancement of the human race will, in no small measure, 

 depend. 



