ON VARIATIONS. 349 



power of procreating offspring. It does not neces- 

 sarily follow, however, that Natural Selection, in the 

 ordinary sense of the term, is at work. The time of 

 death may be quite uncorrelated with any particular 

 structural characters of the body, but be dependent 

 only on the so-called vigour or vitality of the organism. 

 Each subsequent generation may therefore be more 

 " vigorous " than the one before it, owing to the elimi- 

 nation of a portion of the less vigorous individuals, but 

 as, in all probability, there is always a tendency to the 

 production in each generation of a certain number of 

 unfit individuals, or a slight diminution in the average 

 vitality of the whole group, it would follow that a cer- 

 tain amount of elimination is always necessary, to en- 

 able a race to maintain its average vitality from one 

 generation to the next. Certainly, in the case of the 

 human race, there is no evidence that the average 

 vigour and vitality are increasing. Everything goes 

 to prove rather that they are on the wane. 



Man is therefore an unsatisfactory organism in which 

 to determine either the existence or the non-existence 

 of Natural Selection. His conditions of death are as 

 unnatural as his conditions of life. The usual cause 

 of his death, disease, counts for little or nothing 

 amongst the lower animals, whilst the usual causes of 

 death amongst them, namely, want of food and natural 

 enemies, count for little or nothing with man. To 

 prove the existence of Natural Selection, one must 

 choose for observation an organism living under nat- 

 ural conditions. 



A very interesting case of the formation of a local 

 race through the probable agency of Natural Selection 



