4 HEREDITY AND SEX 



quickly made good, for delay, if prolonged, would 

 increase the chances of death. 



But there is another method of division that is almost 

 universal and is utihzed by high and by low forms alike : 

 individual cells, as eggs, are set free from the rest of 

 the body. Since they represent so small a part of the 

 body, an immense number of them may be produced on 

 the chance that a few will escape the dangers of the 

 long road leading to maturity. Sometimes the eggs 

 are protected by jelly, or by shells, or by being trans- 

 parent, or by being hidden in the ground or under 

 stones, or even in the body of the parent. Under these 

 circumstances the animal ventures to produce eggs with 

 a large amount of food stored up for the young embryo. 



So far reaching were the benefits of reproduction 

 by eggs that it has been followed by almost every 

 species in the animal and plant kingdom. It is ad- 

 hered to even in those cases where the animals follow 

 other grosser methods of separation at the same time. 

 We find, however, a strange limitation has been put 

 upon the process of reproduction by eggs. Before the 

 egg begins its development it must be fertilized. Cells 

 from two individuals must come together to produce 

 a new one. 



The meaning of this process has baffled biologists 

 ever since the changes that take place during fertili- 

 zation were first discovered ; in fact, long before the 

 actual processes that take place were in the least un- 

 derstood. There is a rather extensive and antiquated 

 literature dealing with the part of the male and of 

 the female in the process of procreation. It would 

 take us too far to attempt to deal with these questions 



