44 DEGENERA TION. 



was tattooed like a New Zealander, carried the 

 weapons of a New Zealander, and, over and above in 

 addition to these proofs, that he talked the Maori 

 language and none other ; so here, in the case of 

 the vertebrate race, there are certain qualities and 

 possessions, the accumulation of which cannot be con- 

 ceived of as occurring in any animal but one belonging 

 to that race. These four great structural features are 

 — first, the primitive backbone or notochord ; second, 

 the throat perforated by gill-slits ; third, the tubular 

 nerve-centre or spinal cord and brain placed along the 

 back ; and lastly, and perhaps most distinctive and 

 clinching as an evidence of affinity, the myelonic or 

 cerebral eye. 



Now let us convince ourselves that these four 

 features exist not only in the frog's tadpole, as 

 they do in all fishes, reptiles, birds, and beasts, but 

 that they also exist in the Ascidian tadpole, and, 

 it may be added, co-exist in no other animals at all. 



The corresponding parts are named in Figs. i6 

 and 17, in such a way as to render their agreement 

 tolerably clear, whilst in Fig. 18 a more detailed 

 representation of the head of an Ascidian tadpole 

 is given. 



