254 THE EVOLUTION OF MAN. 



without any trace of external appendages, without any 

 division of the body into head, neck, breast, abdomen, etc. 

 Its whole form is so simple, that its first discoverer declared 

 it to be a naked Snail. Not until much later (about forty 

 years ago) was the remarkable little being more closely 

 examined, and it then became evident that it is a true 

 Vertebrate. Later investigations have shown that its bearing 

 on Comparative Anatomy and human Embryology and 

 Phylogeny is of the higliest importance. For the Lancelet 

 enables us to solve the weighty question as to the descent 

 of Vertebrates from Worms, with certain lower forms 

 (Ascidia) of which it is immediately connected in its de- 

 velopment and bodily structure. 



Now, if we make several sections through the body of 

 the Amphioxus, — first, perpendicular longitudinal sections 

 through the whole body from front to back, and secondly, a 

 perpendicular cross-section through it from right to left, we 

 shall obtain two instructive anatomical pictures. (Cf Plates 

 X. and XI.) In aU essential points they correspond to the 

 abstract ideal, which, aided by Comparative Anatomy and 

 Ontogeny, we are able to conceive as the primitive type, 

 as the picture of the Primitive Vertebrate ; of that long 

 extinct parent-form, to which the whole Vertebrate tribe 

 owes its origin. We need only make very slight and im- 

 material alterations in the actual sections of the Amphioxus, 

 in order to obtain such an ideal anatomical picture or 

 diagram of the primitive form of the Vertebrate, as it is 

 represented in Fig. 52-56. The Amphioxus differs so 

 little from this primitive form that it may be accurately 

 described as a Primitive Vertebrate. (Cf Plates X. and XI. 

 with Fig. 52-56.) «5 



