196 DARWINISM AND HUMAN LIFE 



organisms have to considerable accumulations of 

 their own seK-made poisons or waste-products ? 



To illustrate adaptations Weismann takes, for 

 instance, the whale-type among mammals, and 

 refers to " the fish-Uke form of the body, the 

 hairlessness of the skin, the transformation of 

 the fore-limbs to flippers, the disappearance of 

 the hind-Umbs and the development of tail-flukes, 

 the layer of blubber under the skin, which afiords 

 the protection from cold necessary to a warm- 

 blooded animal," and so on through a long hst. 

 The whale is a great bundle of adaptations to 

 a mode of Ufe which is pecuhar for a mammal. 



Whether we take actively functional parts, 

 such as our own hand, or passively functional 

 structures, such as a feather ; whether we take 

 obvious features, such as the tjrpical spindle-Hke 

 shape of fishes, or more recondite features, such as 

 the structure of a bone ; whether we take mimicry 

 / or migration, " wherever we tap organic nature," 

 I as Romanes said, " it seems to flow with purpose." 



Natural selection is the theory of the indirect 

 coming about of this wide-spread puiposefulness— 

 the possibility of variations in the direction of 

 fitness being granted. Lamarckism, which assumes 

 the hereditary accumulation of functional and 

 environmental modifications, is a theory of direct 

 adaptation — on the whole simpler than the selection 

 theory, but suffering from the serious disadvantage 

 that its fundamental assumption is stiU without 

 cogent evidence in its favour. 



Birds' eggs are of diverse shapes, and we know 

 in some detail the actual factors which determine 

 these. We also know that individual variations 

 in the shape are not uncommon. We can under- 



