420 THE WONDER OF LIFE 



not even fertiKzed. The race is continued because there 

 are so many. 



One must never think of Nature as dehberating and 

 deciding to replace a wasteful process by a more economical 

 one, nor yet as simply drawing her bow at a venture and 

 in the course of time hitting a mark. What goes on is 

 a ceaseless experimenting in different modes of self- 

 expression. Less prohfic forms arose, and those that in- 

 stinctively took some care of eggs or offspring tended to 

 define the direction of evolution. Sometimes, on the other 

 hand, more careful types arose — resting exhausted beside 

 their mass of eggs, and by and by incubating them— and 

 those that were more economical in productivity would 

 tend to define the direction of evolution. The process 

 may have worked either way. 



A number of suggestions may be offered. (1) The 

 passage from aquatic to terrestrial life is associated with 

 internal fertilization and with the suppression of larval 

 stages (see Chapter II), and it foUows that the mother 

 animals would come to have a longer organic acquaintance 

 with their ova. The bird laying her eggs is much more 

 aware of what she is doing than the fish in the sea. (2) 

 In certain conditions, such as the low temperature of the 

 abysses or of polar seas, growth processes are slowed. This 

 might lead to a longer retention of the ova within the body, 

 and to viviparity. It is very significant that in Antarctic 

 Bchinoderms, for instance, there is a general, though not 

 complete suppression of free-swimming larval stages, and 

 many cases are known of parental care, differing curiously 

 in details. (3) As is usual, when we face such problems, 

 we find that there are many approaches to parental care 

 and family hfe. The goal was probably reached very 



