MAMMALIAN DAWN. 85 



assigned to one or another of them, while from the Middle 

 Tertiary on the ancestral lines -can be more or less directly 

 traced. As to the origin of the sub-order Pinnipedia, palae- 

 ontology has as yet furnished no definite clue. Fragmentary 

 remains characteristic of the seal have been obtained from 

 the Pliocene of Europe and North America, and it is known 

 that by this period they had already become well specialized 

 to their aquatic mode of life. It is quite possible that their 

 early Tertiary ancestors were lake-dwelling animals which 

 eventually wandered into the sea. 



The ancient order of Insectivora is of interest in repre- 

 senting more nearly than any other living order the primitive 

 stock from which other mammals have descended, and it is 

 probable that the little insect eating mammals are but slightly 

 altered survivors of some of the earliest placentals. At the 

 dawn of mammalian life this group was of much more 

 importance than now., but they have progressed but little, and 

 their competitors among other mammalian orders have out- 

 stripped them in the struggle for survival. Therefore the 

 Insectivora are a disappearing group which, to escape the 

 severe competition with the better equipped, have taken refuge 

 in peculiar modes of existence or methods of defense, as the 

 earth-l^urrowing mole, the nocturnal and easily concealed 

 little shrew, and the hedgehog with its spiny coat serving as a 

 protective armor. Some of the extinct insectivores and 

 lemurs apparently constitute a link between the Insectivora 

 and Primates. Of the latter order the lemurs of Madagascar 

 are the most primitive, the smallest of monkeys, the little, 

 squirrel-like marmosets, being nearest allied to them. The 

 earliest lemurs, so far as known, lived in Eocene times in 

 Europe and North America, while at the present day the 

 majority of these representatives of the monkey tribe are to 

 be found in that common haunt of weird and archaic beasts, 

 the inipenetral)le forests of Madagascar. 



The study of the successive predominance and subordina- 

 tion in the struggle for existence, up through the respective 



