218 Zoology as Related to Evolution. 



It is a philosophy, moreover, which holds good not only 

 with reference to those species of animals which are in the 

 direct line of man's origin, but in some measure of all the 

 side ones, also, that have branched off from it and ended only 

 in themselves. Mr. Dawson urges it as an argument against 

 Darwinian evolution that the trilobite, after existing all 

 through the Silurian and Devonian ages, finally died out 

 without giving rise to any new forms of life. It is a kind of 

 reasoning which hardly looks further than their own stony 

 eyes. The trilobites did their work and answered the why of 

 their existence by the nutriment they afforded the surviving 

 main stock of animal life. It is a part of the magnificent 

 economy of nature, one of the reconciling features in its hor- 

 rible system of having animals eat each other up, that its 

 very failures are used thereby to make its successes its creat- 

 ures that perish in their struggle for existence are made to 

 live and triumph in those which survive. The distinction 

 between eater and eaten, as we go down the scale of being, 

 grows continually less and less. Eeproduction by nutrition 

 is only the opposite side of reproduction by fission. When a big 

 amoeba eats a small one, the result is a new creature almost 

 as much as when higher up the two parents unite their lives 

 in that of a child. Indeed, there are some cases where the 

 new food is a direct agent in producing a new species. In- 

 heritance in nature is from branches as well as roots, from 

 uncles and aunts as well as from fathers and mothers. The 

 lower limbs of a forest tree are not the less necessary for its 

 growth, nor the less represented in its final fruit, because its 

 top boughs grow on it elsewhere, leaving the bottom ones to 

 be overshadowed and die. And whole species of animals have 

 done the same thing for man's stock in the past that indi- 

 vidual animals and plants are doing now elaborated its food 

 and food qualities out of coarse, inorganic elements up into 

 what was most akin to its own flesh and blood. 



Of course the process has been a very slow one myriads 

 of animals to establish a single habit, ages of time to deposit 



so many and rapid. The truth of the matter seems to be that the two methods 

 of change work together. Nature makes the variation at birth, and then use 

 comes in to establish its functioning as a habit. If the stock is young and vigor- 

 ous, the variation advantageous, and its use continued long enough, then the 

 whole thing, both the original variation and its acquired strength, are transmitted 

 by inheritance, otherwise the reversion is back in the offspring to the channel in 

 which the life stream first flowed. It is precisely what is seen in the individual- 

 acquisitions of knowledge and character much more easily made in childhood 

 than in age, but retained and made a part of their acquirer only by their constant 

 use ; and it is all expressed in the familiar saying that " it is hard to teach an 

 old dog new tricks," the dog being in zoology the species and the race. 



