DR. GADOW AND MISS ABBOTT ON THE VERTE- 

 BRAL COLUMN OF FISHES. 



O. P. HAY. 



IN the Publications of tlie Field Columbian Museum, vol. I, 

 pp. 1-54, the writer issued a paper entitled, " On the Structure 

 and Development of the Vertebral Column of Amia." Before 

 this paper appeared, but after it had passed out of my control, 

 there was printed in the Philosophical Transactions, Royal 

 Society of London, vol. 186, pp. 163-221, a paper by Dr. Hans 

 Gadow and Miss E. C. Abbott, the title of which is, "On the 

 Evolution of the Vertebral Column of Fishes." This is in 

 many respects an excellent treatise, partly on account of the 

 attempt to define accurately many expressions which have been 

 used rather loosely, and to introduce other terms which are 

 more concise than those hitherto employed. The confirmation 

 of Klaatch's results regarding the manner of development of 

 the vertebral centra of sharks is important, as is also the 

 authors' determination of the origin of the elastica externa. 

 The results of their study of Amia are, of course, of interest to 

 myself, and in some respects they anticipated my own conclu- 

 sions. On the other hand, the paper is somewhat marred by 

 a number of typographical errors, by the apparent transposi- 

 tion of paragraphs (p. 175), and by rather unsatisfactory text 

 figures. Aside from these minor defects, the work, it seems to 

 me, is pervaded by an erroneous theory concerning the origin 

 of the skeletogenous tissue and the perichordal cartilages. 



I will first of all make a remark regarding the definitions of 

 the two kinds of vertebral centers recognized by Dr. Gadow 

 and Miss Abbott. They animadvert on Kolliker's terms 

 "chordal centra" and " perichordal centra "; but the chordal 

 sheath, being a product of the notochord, might not improperly 

 be regarded as a part of the notochord itself ; and then Kolli- 

 ker's names would be appropriate. On the other hand, our 

 authors proceed to say that the centra of the higher Vertebrata, 



