THEORIES OF EVOLUTION 17 



in endurance, speed, sight, scent, hearing, taste, digestion, 

 and so forth. 



28. As in the case of the Lamarckian doctrine it will be 

 useful to note a few points in reference to the Darwinian 

 theory. As already mentioned, variations are seldom great 

 abnormalities, but, as a rule, small deviations from the parental 

 type. Thus a man's hand may differ from his father's hand 

 in having a sixth digit ; but more commonly it is merely 

 larger or smaller, stronger or weaker, finer or coarser. By 

 shape and texture it may be more or less fitted to a particular 

 kind of work ; or it may be more or less capable of adapting 

 itself to new conditions e. g. by acquiring protective callosities 

 of the skin when a change is made from light use to heavy 

 manual labour. The various structures of living beings are 

 so nicely adapted to one another, and living beings themselves 

 are so closely fitted to their environments that a great 

 variation (i. e. abnormality) can very seldom if ever be other 

 than harmful. Indeed it is probable that no instance of an 

 abnormality useful to a plant or animal in a state of nature 

 has been recorded. It was assumed by Darwin, therefore, 

 and in this his modern followers as a rule agree with him, 

 that evolution through the agency of Natural Selection 

 proceeds on lines of small variations, not on lines of great 

 abnormalities. They suppose that all structures, no matter 

 how large and complex, began originally as small variations of 

 pre-existing structures, and that they were evolved in succeed- 

 ing generations by the continued addition of small variations. 

 Thus they suppose that, when the hornless ancestors of deer 

 began to push one another with their foreheads, the animals 

 with the thicker and stronger frontal bones were, other things 

 equal, the more successful in the struggle for mates. Next 

 through the survival of the fittest, by the accumulation of 

 normal variations, small bosses of bone were gradually evolved 

 on the thickened skulls. Lastly, still by the accumulation 

 of normal variations, antlers appeared and increased in size 

 till their further enlargement was no longer useful. 



29. To take another extreme case : According to Neo- 

 Darwinians it is not necessary to postulate a great abnor- 

 mality as the starting-point of wings. The fins of flying-fish, 

 which may easily have evolved without the aid of abnor- 

 malities from smaller organs, have reached a stage from 

 which, still without abnormalities, they may as readily evolve 

 into organs for more sustained flight. And did this happen, 

 and were it accompanied by equally gradual changes in other 

 structures, the species would ultimately become adapted to an 



