ADAPTIVENESS AND PURPOSIVENESS 321 



Of great interest are the co-ordinating functional adjust- 

 ments which secure smooth working. A fine example is the 

 heat-regulating arrangement or therrnotaxis of birds and 

 mammals, which adjusts the production of animal heat so 

 as to meet the loss. Superimposed on this, as it were, are 

 the special adjustments which bring about winter-sleep in 

 hibernating mammals. And there is no internal regulation 

 more worthy of our admiration than the manner in which 

 the mother-mammal is functionally prepared for the ante- 

 natal development of the offspring and its nurture after birth. 

 The adaptive regulatory role of the internal secretions is 

 one of the most fascinating chapters in modern physiology. 



Inexhaustible, again, are the illustrations of the manner 

 in which living creatures are adapted to the particular con- 

 ditions of their life. The mole, living underground, is 

 adapted in its short vertical fur and in the absence of an 

 ear-trumpet to the reduction of friction in burrowing; its 

 hand has become an extraordinary shovel and its shoulder- 

 girdle and associated musculature are powerfully developed; 

 the minute, imperfectly developed eye is good enough for 

 what is required of it, and it is hidden by hair so that it 

 does not get rubbed and become a source of weakness; and 

 so the zoologist goes on. 



We may also refer to the theoretically very interesting 

 inter-organismal adaptations. These may be between or- 

 ganisms of the same kind, between parent and offspring, 

 between male and female. Even the male parent may be 

 adapted to the offspring as we see in the pouch of the 

 sea-horse, and in the still more striking case of the New 

 Guinea fresh-water fish called Kurtus, where a hooked bony 

 process grows from the top of the male's head at the breed- 

 ing season and serves for the suspension of the bunch of 



