VERTEBRATION OF THE TAIL OF APPENDICULAR!^. 387 



The Vertebration of the Tail of Appendicular!^. 

 By E. Ray Lankester, M.A., F.R.S. 



A PROMINENT objection to the association proposed by me 

 of the Tunicata as a subdivision " Urochorda '' with the " Ce- 

 ])halochorda "" ( Amphioxus) and the " Craniata " in one group, 

 for which the name " Vertebrata" is retained, has been the fact 

 especially put forward by Gegenbaur, that the Urochorda 

 (Tunicata) do not exhibit any " vertebrate " structure, that is 

 to say, a division of the body into myotomes. Eor a similar 

 reason Balfour, whilst accepting the three-fold division of the 

 Vertebrata, has proposed to denominate that group " Chor- 

 data," and to restrict the term Vertebrata to the craniate division 

 of the Chordata, thus excluding the Cephalochorda, as well as 

 the Urochorda from the application of the term " vertebrate " 



The best way of indicating the relationship of the Tunicates to 

 the forms usually recognised as " Vertebrata " appears to me to 

 consist in introducing the Tunicata or Urochorda into the long- 

 established and familiarly known group of Vertebrata, in ac- 

 cordance with our improved knowledge as to the actual struc- 

 ture of the former, and not in making a new group with a 

 new name, whereby the significance of the association is, to a 

 large extent, lost. 



So far as the term " vertebrate " is concerned, we might, 

 of course, legitimately disregard its signification. There is 

 no reason why some Vertebrata should not be inaccurately de- 

 scribed as "vertebrate," just as some Arthropoda are not 

 arthropodous, some Chsetopoda not chsetopodous, and some 

 Gastropoda not gastropodous. 



On the other hand, if we accept the term *' vertebrate " not 

 as implying the possession of bony or cartilaginous vertebrae 

 (as Balfour proposed), but as meaning "jointed" or " meta- 

 merised," then it appears that even amongst the Urochorda or 

 Tunicata, facts justifying its use in relation to them may be 

 discovered. 



Apart from the verbal question, it is a matter of some im- 

 portance that indications of metamerised structure should occur 

 in the Urochorda. 



VOL. XXII. NEW SER. C C 



