THE S T AND POINT OF BIOLOGISTS. 23 



Three Ideas involved in Selection. 



Now there are three ideas in this law of natural 

 selection: first, that there are inborn variations among 

 the offspring even of the same family ; secondly, that 

 these various individuals living in surrounding con- 

 ditions on the whole uniform and common to all of 

 them, will start in life, some with an advantage and 

 others with a relative disadvantage, and that those 

 possessing an advantage will, more of them, tend to 

 produce offspring ; thirdly, that the variations, inborn 

 in this case and not acquired, will probably be trans- 

 mitted. That there are marked variations physical, 

 mental, and moral among a litter of kittens or 

 puppies is within the experience of everyone who has 

 kept them, and that variations in human families are 

 as marked is known to everyone who has brothers 

 and sisters. Even twins frequently differ consider- 

 ably from each other, and it is said that the last 

 years of the lives of the Siamese twins were sadly 

 marred by their opposing views as to the rights and 

 wrongs of the American Civil War! It stands to 

 reason also that these variations may be of advan- 

 tage or disadvantage to their possessors, and that 

 among animals and plants, where there are no social 

 props given to the weak, the variations may and do 

 determine survival. To give an idea of the rigorous 

 operation of selection which we find among the lower 



