8o EVOLUTION IN THE PAST 



With primitive lizards, crocodiles, dinosaurs, plesiosaurs,. 

 " fish-lizards," and tortoises on the scene, there was, it must 

 be admitted, a wonderful display of reptile life. But these 

 creatures, although highly and variously developed, were 

 not at least in the latter part of the Period the highest 

 life-forms on earth : for at that time Mammals were certainly 

 in being. 



MAMMALS It is not possible to picture the appearance of these 

 prototheres or " first beasts " as they are named ; for there 

 is nothing to recall them save some jaws and teeth, and a few 

 bones, found in Europe and North America (Dromatherium, 

 Micronodon, Microlestes). They do not appear to have been 

 larger animals than rats and mice. Some of them were 

 probably constituted like the Australian ant-eater (Echidna), 

 laid eggs, and nourished their young with milky juice oozing 

 from the breast ; whilst others probably brought forth 

 young of minute size, and carried them about in pouches 

 after the manner of marsupials. 



These primitive creatures must have been in frequent 

 danger from carnivorous reptiles ; but they doubtless sur- 

 passed reptiles in some important respects. Reptiles, as a 

 rule, are sluggish animals ; their brain power is of humble 

 calibre ; and their morality, as judged by the little or no 

 care they exhibit for their offspring, is equally low-pitched. 

 And it is probable that the Triassic reptiles had similar 

 shortcomings. On the other hand, these primitive mammals 

 were probably nimble and active little creatures, with a 

 relatively high intelligence, and keenly solicitous for the 

 welfare of their young. These attainments were bound to 

 tell in time, unless creation rested simply on brute force. 



" Whence," one may naturally ask, " were these types of 

 higher life evolved ? " There is little or no doubt they were 

 evolved from reptiles, probably from some very small " beast- 

 shaped " forms (Theromorphs) ; and from such of those as 

 had teeth of a more or less mammalian pattern (Theriodonts). 

 At least no other descent so probable as this can be given. 



The appearance of mammals was indeed an event of the 

 highest significance. Nature after successive stages from 

 marine invertebrates to fishes, amphibians, and reptiles, 



