Classification of Fishes 383 



Dr. Gill observes: "Perhaps there are no words in science 

 that have been productive of more mischief and more retarded 

 the progress of biological taxonomy than those words pregnant 

 with confusion, High and Low, and it were to be wished that 

 they might be erased from scientific terminology. They de- 

 ceive the person to whom they are addressed. They insen- 

 sibly mislead the one who uses them. Psychological prejudices 

 and fancies are so inextricably associated with these words 

 that the use of them is provocative of such ideas. The words, 

 generalized and specialized, having become almost limited to 

 the expression of the ideas which the scientific biologist wishes 

 to unfold by the others, can with great gain be employed in 

 their stead." (" Families of Fishes," 1872.) 



The Problem of the Highest Fishes. As to which fishes 

 should be ranked highest and which lowest, Dr. Gill gives (" Fam- 

 ilies of Fishes," 1872) the following useful discussion: "While 

 among the mammals there is almost universal concurrence as 

 to the forms entitled to the first as well as the last places, nat- 

 uralists differ much as to the 'highest' of the ichthyoid verte- 

 brates, but are all of one accord respecting the form to be desig- 

 nated as the 'lowest.' With that admitted lowest form as a 

 starting-point, inquiry may be made respecting the forms which 

 are successively most nearly related. 



" No dissent has ever been expressed from the proposition 

 that the Leptocardians (Branchiostoma) are the lowest of the 

 vertebrates; while they have doubtless deviated much from 

 the representatives of the immediate line of descent of the 

 higher vertebrates, and are probably specialized considerably, 

 in some respects, in comparison with those vertebrates from 

 which they (in common with the higher forms) have descended, 

 they undoubtedly have diverged far less, and furnish a better 

 hint as to the proto vertebrates than any other form. 



" Equally undisputed it is that most nearly related to the 

 Leptocardians are the Marsipobranchiates (Lampreys, etc.), 

 and the tendency has been rather to overlook the fundamental 

 differences between the two, and to approximate them too 

 closely, than the reverse. 



" But here unanimity ends, and much difference of opinion 

 has prevailed with respect to the succession in the system of the 



