Fig. I. 



The Lancelet {Amphioxus), the supposed earli- 

 est type of vertebrate animal, and, according to 

 Haeckel, the ancestor of man. The figure is a sec- 

 tion enlarged to twice the natural size. 



a, mouth; 



by anus; 



c, gill- opening; 



• d, gill; 



e, stomach; 

 /, liver ; 

 g, intestine; 

 h, gill-cavity; 



i, notochord, or rudimentary back-bone; 

 ^> /. m, n, 0, arteries and veins. 



«}' 



63 



