EVOLUTION. 8 1 



than others. These are sometimes termed pre-pote7it, and, as a general 

 rule, the male is probably pre-potent over the female. A peculiar form 

 of heredity of very doubtful occurrence is Telegouy. If a high-bred 

 bitch have a litter to a mongrel it is a commonly accepted tradition 

 amongst breeders that future litters, although to high-bred dogs, will be 

 contaminated by mongrel characters. There is at present no definite 

 evidence for the occurrence of telegony. 



But heredity is not confined to parents or others of the preceding 

 generation. Many structural characters are transmitted to the second 

 generation leaving the intermediate generation apparently unaffected. 

 Insanity is a remarkable instance of this. 



Lastly, an individual may exhibit characters which resemble its more 

 remote ancestors. These characters are, of course, variations from the 

 point of view of the parents and are often termed atavistic. 



The term Reversion is also used to describe this phenomenon as well 

 as the wider return of a whole species to ancestral structure (see Coluviba). 



Evolution. — If we apply the principle of heredity to 

 the whole animal kingdom we are led to explain the 

 structural similarity of genera, orders, classes, and phyla as 

 due to a common descent from the same early types. The 

 process of descent with modification is called Evolution^ 

 and hence an evolutionist is one who holds that all living 

 animals are genetically connected in the past. 



Assuming this to be the case, how can this descent or 

 evolution have been effected ? If we are able to show that 

 one species can, under certain conditions, evolve into 

 another, the same argument will apply to the higher grades, 

 such as genera, orders, &c. If there were no variation, 

 each generation of a species would by heredity be like its 

 predecessor and no structural change could be effected. 

 But we have seen that, owing to variation, the offspring 

 never quite resembles its parents, and it is evident that 

 if these differences could be accentuated and made per- 

 manent, an eventual transformation of the species could 

 be. effected. 



Darwin was the first to show that there are certain 

 conditions in nature which make this actually possible. 

 Starting with the first principle of variation, as stated 

 above, he went on to show that all animate nature tends to 

 reproduce itself at a far higher rate than the available means 

 of subsistence. This is the direct cause of the struggle for 

 existence. Every animal in nature has to struggle for its 

 very means of subsistence with other animals and above all 

 M. 7 



