Classification of Fishes 379 



Meaning of Species. Quoting once more from the admirable 

 essay of Dr. Coues on the taxonomy of birds: "The student 

 cannot be too well assured that no such things as species, in the 

 old sense of the word, exist in nature any more than have 

 genera or families an actual existence. 

 Indeed they cannot be, if there is 

 any truth in the principles discussed 

 in our earlier paragraphs. Species 

 are simply ulterior modifications, 

 which once were, if they be not still, 

 inseparably linked together ; and their 

 nominal recognition is a pure con- 

 vention, like that of a genus. More 

 practically hinges upon the way we F ~ 245.-Hornless Tnmkfish 

 regard them than turns upon our es- tf ace-view), iMctophrys trigonus 



f ... , , , . , . (Linnaeus). Charleston, S. C. 



tablishment of higher groups, simply 



because upon the way we decide in this case depends the scien- 

 tific labeling of specimens. If we are speaking of a robin, we 

 do not ordinarily concern ourselves with the family or order it 

 belongs to, but we do require a technical name for constant use. 

 That name is compounded of its genus, species, and variety. 

 No infallible rule can be laid down for determining what shall 

 be held to be a species, what a conspecies, subspecies, or variety. 

 It is a matter of tact and experience, like the appreciation of 

 the value of any other group in zoology. There is, however, a 

 convention upon the subject, which the present workers in or- 

 nithology in this country find available ; at any rate we have no 

 better rule to go by. We treat as "specific" any form, how- 

 ever little different from the next, that we do not know or be- 

 lieve to intergrade with that next one, between which and the 

 next one no intermediate equivocal specimens are forthcoming, 

 and none, consequently, are supposed to exist. This is to imply 

 that differentiation is accomplished, the links are lost and the 

 characters actually become "specific." We treat as "varietal" 

 of each other any forms, however different in their extreme 

 manifestation, which we know to intergrade, having the inter- 

 mediate specimens before us, or which we believe with any good 

 reason do intergrade. If the links still exist, the differentiation 



