76 Animal Life and Intelligence. 



area, the conditions of which are not undergoing change, 

 the numbers of the species which constitute its fauna 

 remain tolerably constant. They are not actually increasing 

 in geometrical progression. There is literally no room for 

 such increase. The large birth-rate of the constituent 

 species is accompanied by a proportionate death-rate, or 

 else the tendency is kept in check by the prevention of 

 certain individuals from mating and bearing young.* 



Now, the high death-rate is, to a large extent among 

 the lower organisms and in a less degree among higher 

 animals, the result of indiscriminate destruction. When 

 the ant-bear swallows a tongue-load of ants, when the 

 Greenland whale engulfs some hundreds of thousands of 

 fry at a gulp, when the bear or the badger destroys whole 

 nests of bees, in such cases there is wholesale and indis- 

 criminate destruction. Those which are thus destroyed are 

 nowise either better or worse than those which escape. At 

 the edge of a coral reef minute, active, free-swimming coral 

 embryos are set free in immense numbers. Presently they 

 settle down for life. Some settle on a muddy bottom, 

 others in too great a depth of water. These are destroyed. 

 The few which take up a favourable position survive. But 

 they are no better than their less fortunate neighbours. 

 The destruction is indiscriminate. So, too, among fishes 



* More observations and fuller knowledge on this latter point and on the 

 relative numbers of the sexes in different species are much to be desired. It 

 is clear that the number of offspring mainly depends upon the number of 

 females. But if it be true that good times and favourable conditions lead 

 to an increased production of females, while hard times and unfavourable 

 conditions lead to a relative increase of males, then it is evident that good 

 times will lead to a more rapid increase and hard times to a less rapid increase 

 of the species. Suppose, for example, in a particular district food and other 

 conditions were especially favourable for frogs. Among the well-nourished 

 tadpoles there would be a preponderance of females. In the next generation 

 the many females would produce abundant offspring (for one male may 

 fertilize the ova laid by several females). There would be a greater number 

 of tadpoles to compete for the same amount of nutriment. They would be 

 less nourished. There would be less females ; and in the succeeding genera- 

 tion a diminished number of tadpoles. Thus to some extent a balance between 

 the number of tadpoles and the amount of available nutrition would be main- 

 tained. These conclusions are, perhaps, too theoretical to be of much value, 

 while the tendency here indicated would be but one factor among many. 



