THE EVOLUTION OF MAN 



of these three classes from the other, and it is 

 still less feasible to fit the vertebrates into any 

 one of them. It would be impossible to develop 

 an Amphioxus from a star-fish or an octopus. 

 Some have attempted a theoretical line of descent 

 from crustaceans to fish, but only by means of 

 such a yawning chasm that no rational investi- 

 gator went with them. The difference between 

 these things is too great. 



On the other hand, it is remarkable that all 

 those groups may easily be traced back, each by 

 itself, to some higher worm. It is true that the 

 worm type to which the line of crustaceans and 

 insects attaches itself and to which, for instance, 

 our leeches and earth worms belong, is very dif- 

 ferent from an ascidian. Evidently there has 

 been a great deal of individual evolution within 

 the higher worm type. But nevertheless this 

 picture presents a great deal of probability. The 

 higher type of worm branched out into insects, 

 mollusks, echinoderms and vertebrates, and it had 

 four possibilities of evolution, among which only 

 the vertebrate was destined to win the crown 

 the form of man. But this entire stage of worm 

 life proceeded from some still lower worm which 

 would therefore represent the next common sta- 

 tion of all worms, and with them all men. 



116 



