REPRODUCTION AND SEX 197 



parent. It would seem that this may happen in two ways. 

 In many cases the tendencies inherited from the two 

 parents, when they differ, do not counteract one another, 

 but, in respect of a given character of the animal in question, 

 such as the size, or shape, or colour, or texture of any part 

 of the body, one or other of the parents is dominant, the 

 legacy from the other being latent or recessive, so that the 

 offspring will "take after" one parent. This dominance 

 belongs to one parent in respect of some characters and to 

 the other in respect of others, so that every conjugation 

 brings about a reshuffling of the characters, and the young is 

 not exactly like either parent. In regard to other characters 

 the tendencies inherited from the two parents do appear to 

 counteract one another, so that by conjugation these 

 characters of the offspring become a mean of those of the 

 parents. In this case also there will be a difference 

 between the two generations. Thus it comes about that 

 no two members of a species are identical in their 

 characters. A change in the conditions of life — as of food, 

 temperature, enemies, and so forth — is thereby more likely 

 to find individuals adapted to cope with it and continue 

 the species, and this, according to one view, is the advantage 

 derived from conjugation. (V) Another result of the con- 

 jugation of germs derived from different parents is to 

 prevent the formation of strains descended each from a 

 single parent. Thus, while it is continually making new 

 kinds of individuals, conjugation is also preventing any of 

 them from becoming permanent. It is by some held that 

 this is of advantage, in that the members of the species are 

 by it prevented from becoming specialised in a way that 

 would put them out of harmony with the conditions under 

 which they have to live. It is possible that conjugation is 

 beneficial to the organism in both these ways, but self- 

 fertilisation is an obstacle to any theory which regards 

 the consequences of the process in heredity as its sole 

 function. 



Whether or not any of these interpretations of the 



meaning of conjugation be the correct one, 



there can be no doubt that it is a process of 



the highest importance to the organism. If by nothing 



else, this is shown by the fact that the whole mechanism 



