102 ANIMALS OF NO IMPORTANCE. 



To answer this question one must, perforce, wax philo- 

 sophical. Nature knows one way only of developing an 

 organism. It has to tread the path traversed by its ances- 

 tors. Its development is a recapitulation, more or less 

 complete, of the evolutionary stages through which its 

 forefathers have passed. In a few short weeks the develop- 

 ing animal covers ground over which its progenitors 

 required hundreds of thousands of years to tread. The 

 fierceness of the struggle for existence has forced on Nature 

 the necessity of making development as rapid as possible. 

 The life-history of every animal falls into two periods. In 

 the first the organism is shielded from the universal strug- 

 gle or, at any rate, takes no part in it ; in the second, it 

 has to fight its way or perish. It is obviously for the 

 benefit of the individual that the former period should be 

 as long as possible, for the more highly developed an animal 

 be at birth the better account of itself will it give in the 

 struggle for existence. On the other hand, it is to the 

 advantage of the species that this period be short, for, if 

 the eggs develop outside the mother, the more rapidly they 

 give rise to young animals the less will be their risk of 

 destruction. If the young develop within the mother, the 

 shorter the embryonic period the greater the number of suc- 

 cessive offspring the female can produce in her lifetime. 



Hence a balance has to be struck. The result is a short 

 embryonic period, but a highly developed animal at birth, 

 an animal in most cases able to maintain itself. This organ- 

 ism, however, although able to take care of itself, is often 

 very far from exactly resembling its parent. This will 

 come later. The first necessity is the rapid development 

 of an individual capable of fending for itself. If the 

 creature resemble the parent, so much the better 1 ; if it do 

 not, it will have to undergo the transition while earning its 

 living and thus pass through a stage of hobbledehoyism. 

 The tadpole can be evolved in a few hours from frog's 

 spawn ; but the making of an adult frog requires several 

 weeks ; and if the eggs were exposed defenceless all this 



