Organic Evolution. 189 



successful candidates beats the senior on the list of failures 

 we do not know. We can only see that, on the hypothesis 

 of natural selection, it must have been sufficiently ap- 

 preciable to determine success or failure. 



(4) And then, to come to our fourth point, we must 

 remember that, apart from the differentiating process of 

 elimination, there is much fortuitous destruction. A 

 hundred are born, and but two survive. But of the ninety- 

 eight which die, and fail to procreate, how many are 

 eliminated, how many are fortuitously destroyed, we do 

 not find it easy to say. And indiscriminate destruction 

 gets rid of good, bad, and indifferent alike. It is a mistake 

 to say that of the hundred born the two survivors are 

 necessarily the very best of the lot. It is quite possible 

 that indiscriminate destruction got rid of ninety of all sorts, 

 and left only ten subject to the action of a true elimina- 

 tion. " In the majority of birds," says Professor Weis- 

 mann, "the egg, as soon as it is laid, becomes exposed to 

 the attacks of enemies ; martens and weasels, cats and 

 owls, buzzards and crows, are all on the look out for it. 

 At a later period, the same enemies destroy numbers of the 

 helpless young, and in winter many succumb in the struggle 

 against cold and hunger, or to the numerous dangers which 

 attend migration over land and sea — dangers which decimate 

 the young birds." There is here, first, a certaiij amount 

 of fortuitous destruction ; secondly, some selection applied 

 to the eggs ; thirdly, a selection among the very young 

 nestlings ; and, fourthly, a selection among the young 

 migratory birds. What may be the proportion of elimina- 

 tion to destruction at each stage it is difficult to say. 

 Among the eggs and fry of fishes fortuitous destruction 

 probably very far outbalances the truly differentiating 

 process. 



T?anmixia and Disuse, 



We may now pass on to consider shortly some of the 

 phenomena of degeneration, and the dwindling or dis- 

 appearance of structures which are no longer of use. 



