224 HOWARD AVERS. [Vol. IV. 



as primitive, and in a certain degree ancestral, conditions of 

 structure. 



The derivation of the vertebrate phylum from some simple 

 type closely approaching Amphioxus, in detail of structure, in 

 almost 1 all its organs, as we know them at the present time, 

 becomes a morphological necessity. Instead of precluding the 

 possibility of establishing the claims of Amphioxus to such 

 position in the phylum, every advance in our knowledge of the 

 life-history of Amphioxus serves only to strengthen such claims. 



It is to be regretted that certain zoologists should have so 

 dulled their morphological sense as to be found denying to 

 Amphioxus any position whatsoever among vertebrates. As 

 an offset to such rash opinions, I will only quote the words of 

 Professor Huxley, giving his conclusions after a careful study 

 of the anatomy of Amphioxus, and a detailed comparison with 

 other fish forms : " In all other respects, however, it conforms 

 (except in the absence of auditory organs) to the vertebrate 

 type ; and considering its resemblance to the early stages of 

 Petromyzon, ... I can see no reason for removing it from the 

 class of Pisces." I might quote other eminent authority in 

 favor of the strictly vertebrate nature of Amphioxus, but I think 

 this should sufhce. Surely we may never hope to know more 

 of the mystery of the origin of vertebrates by ignoring the most 

 important of the still accessible forms that lead us back to the 

 beginning of our type. 



It has become necessary, in any discussion of the homologies 

 of the vertebrate brain, to define more accurately what is to be 

 understood by the term ''vertebrate brain.'' Evidently the 

 definition of the word must include the names and relations, 

 as far as lies within the province of a definition, of all those 

 parts common to all vertebrate forms, excluding from the prin- 

 cipal sentence of the definition all exceptions however important. 

 We have not lacked for definitions more or less specific, but 

 until quite recently I do not know of any investigator who has 

 attempted to define the organ in terms harmonious with the 



^ July 27. I have just seen Boveri's paper, " tJber die Niere des Amphioxus " ; 

 and since this investigator has shown in most conclusive manner by his important 

 discovery, that the kidneys of Amphioxus are ancestral structures, I am ready to 

 withdraw the limiting vk'ord "almost," since it was mainly with reference to the 

 kidney system that the reservation was made. 



