HIGH SCHOOL ZOOLOGY. 51 



CHAPTER II. 



Common Forms of Canadian Fish and their Classification. 



1. The common small Catfish, Bull-head oi- Horned pout 

 which we have been examining is known to zoologists as Amiu- 

 rus nebulosus (Le Sueur). Zoologists as well as Botanists use the 

 Linn^an binomial system of nomenclature, which involves the 

 use of a generic and a specific name for the purpose of indicating 

 to what species any individual animal belongs ; of these the 

 generic name stands first, the specific second, and both are 

 followed by the name of the author who first described the kind 

 of animal in question, under that specific name, and (if that 

 should be necessary) by the name of the author who first refer- 

 red the species to its proper genus. The necessity of appending 

 the authoi''s name to a species will be realized when it is under- 

 stood that two different authors may have described individuals 

 of the same species under differsnt names. Thus A. nebulosus 

 has a host of synonymes, one of the most current of which 

 A. catus (Linn.) Gill, is given on the assumption that Linnaeus 

 had already named our Catfish Silurus catus. 



It is veiy hard to find a satisfactory definition for the term 

 "species." In nature we find only individuals; certain groups 

 of individuals resemble each other so closely that we have no 

 hesitation in asserting that they belong to the same si)ecies, 

 others may vary so much in colour or in the pi'oportionate size 

 of different organs or in other ways, that zoologists may hesitate 

 whether or no the individuals exhibiting any constantly associ- 

 ated variations should have a separate specific name accorded to 

 them or merely rank as a "variety." The absence of interme- 

 diate forms between two or njore such groups of individuals is 



