98 THE EVOLUTIONIST AT LARGE. 



an animal whose shape closely resembled 

 that of these wriggling little black creatures 

 which dart up and down like imps through 

 the clear water, and raise a cloud of mud 

 above their heads each time that they bury 

 themselves comfortably in the soft mud of 

 the bottom. But while the birds and beasts, 

 on the one hand, have gone on bettering 

 themselves out of all knowledge, and while 

 the ascidian, on the other hand, in his adult 

 form has dropped back into an obscure and 

 sedentary life sans eyes, sans teeth, sans 

 taste, sans everything the tadpole alone, at 

 least during its early days, remains true to the 

 ancestral traditions of the vertebrate family. 

 \Yhen first it emerges from its egg it repre- 

 sents the very most rudimentary animal with 

 a backbone known to our scientific teachers. 

 It has a big hammer-looking head, and a set 

 of branching outside gills, and a short distinct 

 body, and a long semi-transparent tail. Its 

 backbone is a mere gristly channel, in which 

 lies its spinal cord. As it grows, it resembles 



