140 SECRETS OF EARTH AND SEA 



readable book called " Darwinism," expressed the opinion 

 that the apparent failure of hybrid races to perpetuate 

 themselves by breeding was to a large extent due to the 

 small number of individuals used in experiments on this 

 matter, and the in-and-in breeding which was the con- 

 sequence. One of the great generalizations established 

 by Darwin is that in-and-in breeding is, as a rule, resisted 

 in all animals and plants, and leads when it occurs to a 

 dying-out of the inbred race by resulting feebleness and 

 infertility. A large part of Darwin's work consisted in 

 demonstrating the devices existing in the natural structure 

 and qualities of plants and animals for securing cross- 

 fertilization among individuals of the same species but of 

 different stock. Both extremes seem to be barred in 

 nature — namely, the inter-breeding of stocks so diverse 

 in structure and quality as to be what we call " distinct 

 species," and again the inter-breeding of individuals of 

 the same immediate parentage or near cousinship. What 

 seems to be favoured by the natural structure and qualities 

 of the plant or the animal is that it shall only breed within 

 a certain group — the species — and shall within that group 

 avoid constant self-fertilization or fertilization by near 

 cousins. Thus we find numerous cases in which, though 

 the same flower has both pollen and ovules, and might 

 fertilize itself, the visits of insects (specially made use of 

 by mechanisms in the flower) carry the pollen of one flower 

 to the ovules of another and to flowers on separate plants 

 growing at a distance. It is necessary to note that there 

 are, nevertheless, self-fertilizing flowers, and also self- 

 fertilizing lower animals, the special conditions of which 

 require and have received careful examination and con- 

 sideration, upon which I cannot now enter. 



In relation to the question of the possibility of establish- 

 ing hybrids between various species experimentally, I 

 must (before going on to the cognate question of 



