190 PKOF. JOHN CLELAND, M.D.^ ETC., ON 



classes. I nofe also what is said of the degenei-ate Tunicates, 

 which, in a new edition of the zoological text-book most widely 

 adopted in this country, are set up as a group co-ordinate with 

 the other great branches of the animal kingdom. The chief 

 interest of the paper, to me, is its bearing on " determinate 

 evolution," well illustrated by such fticts as the development of 

 the heart and circulation from Amphibia upward to the crocodile, 

 and prophetic of perfection and use in the higher vertebrates. 



Walter A. Kidd, E^q., M.D., writes : — 



It is well that the Institute should have the opportunit}-, 

 through the able paper of Professor John Cleland, of contributing 

 to that reaction towards the views of Cavier and Owen (called by 

 Professor Huxley "The British Cuvier "), which last year a writer 

 in the Quarterly Review discerned in the scienitific horizon. The 

 Classification of Vertebrata proposed com.mends itself more to the 

 mind not prepossessed with evolutionary doctrines than, foi" 

 example, that of Ray Lankester, who places among the Vertebrate 

 Phylum — 



(1) The Craniata (or Cuvieriau Yertcbr.ita). 



(2) Cephalocnrrla (represented nlone by Amphioxus). 



(3) Urochorda (Tunicata). 



(4) Hemirliorda (Balanoglossus, alone). 



Doubtless the divisions (2) (8) (4) possess those three structures 

 characteristic of Vei'tebi'ata — noto-chord, gill-slits, and dorsal 

 nerve-plates ; but the evidence brought forward by Professor 

 Cleland that the Tunicata are degenerate vertebrates, and the 

 opinion of Professor Alleyne Nicholson that the Amphioxus is 

 usually regarded as a degraded type of the Fishes, make it more 

 correct to place No. (2) No. (3) and (4) in special divisions of the 

 animal kingdom. The late Professor Milnes Marshall admitted 

 that the Tunicata or Ascidians are degenerate animals, but 

 refused to allow this of Amphioxus, saying that it " merely stops 

 at what is an early stage in the development of the higher forms." 

 He is not anxious to claim Tunicata, Balanoglossus, or even 

 Amphioxus, as direct links between the Invertebrate and Verte- 

 brate sub-Kingdoms, but that, of all living animals, Amphioxus 

 most nearly represents the Common Ancestor of Vertebrata. No 

 such half-hearted claims are strong enough for Mr. Edward 

 Clodd in the Primer of Evolution, who boldly claims Amphioxus, 

 Tunicata, and Balanoglossus as interesting links between the two 



