36 "THE COMING OF MAN 



one or two at a season, yet these birds often appear in vast 

 flocks at their remote, solitary and inaccessible nesting places. 

 To reach these breeding-grounds long migrations are often 

 necessary, an important subject into which we cannot enter. 

 The bird will always be an object of fascination both for its 

 attainments and its limitations. Structurally and anatomi- 

 cally as a flying-machine, it is unsurpassed and seems unsur- 

 passable. It disappoints us, perhaps because it is a finished 

 product. It seems to have reached its culmination. Perhaps, 

 as a bird, it is as nearly complete and perfect, as it well can 

 be. 



Mammals are in many ways less interesting than birds. 

 There is nothing spectacular or even very striking in their 

 history. They have always been plodding, slowly progressive 

 forms. 



The skeleton is entirely ossified and well molded and 

 framed, but heavier than in birds. The vital organs are, as 

 a rule, in no way superior to those of birds. Their slower 

 locomotion makes exceeding keenness of sense — except per- 

 haps of smell — less important. Their temperature is lower 

 by some ten degrees Fahrenheit, as we have already seen. 



They started with a covering of scales like those of primi- 

 tive reptiles, from which they seem to be descended. These 

 scales have been retained as a covering for the body in a few 

 forms; and still persist on the tail of some rodents, as the rat. 

 In primitive forms the legs are stout but short, as in most 

 recent reptiles. They laid eggs like reptiles, and this habit 

 is still retained by echidna and platypus in New Zealand. 

 Could we have seen these primitive animals running or shuf- 

 fling over the ground, we could not have considered them very 

 promising. Appearing in the Cretaceous period at the end 

 of Mesozoic time they long remained completely outclassed 

 by the reptiles and began their period of rapid development 

 and rise to supremacy only in Cenozoic time.^ 



^ We may yet return to the older view that, they had appeared in 

 Triassic times. 



