THE ANIMAL ANCESTRY OF MAN - 57 



by means of clothing, houses and the like, to protect his 

 chemical engine from injurious and sudden changes in the 

 surrounding medium. 



As man belongs to the animal rather than to the plant 

 kingdom, he has no chlorophyl-bearing leaves to store up 

 the sun's energy for his use, nor can he derive his raw 

 materials directly from the soil or from the atmosphere, but 

 in common with all other animals he must consume simpler 

 organisms which have already elaborated the raw materials 

 and stored up the energy for him. 



Man is a many-celled animal, or metazoan, and as such 

 each human being consists of a vast and shifting democracy 

 of individual cells, which are organized into cooperative and 

 mutually dependent systems of organs, tissues and the like. 



We need not discuss fully here the still vexed question as to 

 what group of invertebrates the oldest chordate ancestors 

 of man were derived from. It will be sufficient for our present 

 purpose to note that if, with Professors Patten and Gaskell, 

 we try to derive them from the common stem of the arach- 

 nids (scorpions, spiders, etc.) we must conceive that in the 

 transitional stages an entire reorganization was effected, 

 involving radical displacements and transformations of 

 every part of the body. Now while all these changes are 

 clearly conceivable under the terms of the hypothesis, the 

 evidence advanced in support of them has never been accepted 

 by the majority of those best qualified to judge of its value. 

 On the other hand, if we hold with Professor E. B. Wilson 

 and others that the vertebrates belong to that great division 

 of the three-layered animals in which the middle embryonic 

 layer, or mesoderm, arises from pouches lying above the 

 enteron, or primitive gut, then we have to admit that, so 

 far as known at present, the palaeontological record lacks 

 the transitional stages between the vertebrates and their 

 assumed sack-like ancestors and that the vertebrates and 

 the starfish group apparently represent two widely divergent 

 end stages of an unknown common stem. 



CITIZEN MAN OF THE PHYLUM CHORDATA 



At any rate, the "phylum Chordata," to which man and 

 all other vertebrates belong, very early adopted a highly 



