112 REPRODUCTION 



do a certain thing and does it so often as to come to do it 

 readily and without conscious attention we say it has 

 become a habit. If an individual inherits a tendency to 

 do a thing a certain way, and this tendency thus belongs 

 to the whole species we say it is an instinct. Instincts are 

 thus more deeply ingrained into life than habits are. They 

 are not "learned." 



The great vital acts, like feeding, adapting one's self to 

 climatic conditions, and mating and reproducing are 

 surrounded by instincts such as have been described. If 

 an infant is hungry, it instinctively cries and seeks for its 

 food. If a particle of food is placed on the back of its 

 tongue it automatically and instinctively swallows. It is 

 very certain that food-getting, adjustment to cold, mating, 

 and reproduction could not possibly take place in plants 

 and animals with any such precision as we have seen, if 

 it were not for these deep instincts. 



4. Somie of the Instincts Connected with Reproduction. 



The instincts that tend to make reproduction certain and 

 efficient are of three classes: 



(1) The instinct of reproduction itself, which in a 

 purely unconscious way prompts the animal, when it 

 begins to approach maturity, to form the reproductive 

 cells. These are the deepest of all these instincts, indeed 

 they are so deep that we know very little about just how 

 they work. 



(2) The instincts connected with mating, which bring 

 the sex cells together so that they may unite. 



(3) The instincts of caring for the offspring until it is 

 able to care for itself. 



5. The Sex Instincts and Impulses. When minute 

 gametes are produced it is easy to see that it is something 

 of a problem to bring them together and cause them to 

 unite. The simplest instinct connected with mating is the 

 attraction exerted by one gamete on the other. When the 

 female gamete secretes substance in the water, the male 



