GREAT STEPS IN EVOLUTION 97 



dactyls mark the mastery of the air in which 

 Birds and Bats are now most at home. But 

 hardly less impressive is the possessing of 

 every nook and corner. Many a species has 

 only a niche, but it is its own. (6) Following 

 from the masterful, detailed colonization of 

 the heavens and the earth and the waters 

 under the earth, there is the wealth of con- 

 summate adaptation of a creature to its 

 surroundings, to its food, to its habits; of the 

 unborn young to the mother and of the 

 mother to the unborn young; of the sexes to 

 one another; and of the internal architecture 

 of the body, whether in the fit adjustment of 

 the proportions of parts, or in the minute 

 structure of a bone. Every creature is a 

 bundle of adaptations. Indeed, as Weis- 

 mann says of the whale, "When we take 

 away the adaptations, what have we left ? " 

 It is instructive to look into the matter in 

 detail, and to notice, for instance, what types 

 made particular acquisitions. Hag fishes 

 and lampreys (Cyclostomes) were the first 

 animals with skulls; fishes were first with 

 jaws; amphibians gained fingers and toes, 

 true lungs, a voice, and a mobile tongue; 

 reptiles first show the important antenatal 

 robes (or fcetal membranes) called the amnion 

 and the allantois, and the crocodile was the 

 first creature with a four-chambered heart; 



