312 Canadian Record of Science. 



embryonic development, larval development, general considerations,. 

 Amphioxus and Ammoco?tes. 



IV. The Ascidians, including structure of a simple Ascidian, 

 development of Ascidians, metamorphosis of Ciona intestinalis. 



V. The protochordata in their relation to the problem of vertebrate 

 descent. 



This outline of the ground covered will show how complete the 

 work has been made. 



The book is well printed and admirably illustrated by a large 

 number of cuts. The outcome of the entire series of studies on this 

 subject, of absorbing interest to the biologist who believes in evolution, 

 is stated in the final paragraph of the book, which we quote entire : 

 " For the present we may conclude that the proximate ancestor of the 

 vertebrates was a free-swimming animal intermediate in organization 

 between an Ascidian tadpole and Amphioxus, possessing the dorsal 

 mouth, hypophysis and restricted notochord of the former, and the 

 myotomes, ccelomic epethelium, and straight alimentary canal of the 

 latter. The ultimate or primordial ancestor of the vertebrates would,, 

 on the contrary, be a worm-like animal whose organization was 

 approximately on a level with that of the bilateral ancestors of the 

 Echinoderms." 



Wesley Mills. 



