INTKODUCTION. v 



the same species could be compared together, the amount of variability 

 to which one species may be liable could not be properly appreciated. 



We have arrived at the conclusion that only five genera can be 

 distinguished. Of these Icticyon, Lycaon, and Otocyon each contain 

 but one species, while Cyon may be taken as consisting of two. All 

 the rest of the Canida we place in the typical genus Canis. Such 

 animals as the Common Fox and the Fennec would seem at first sight to 

 be without any doubt generically distinct from the Jackal and the Wolf. 

 Nevertheless, when all the series of intermediate forms are examined, 

 the difficulty of drawing any valid generic distinction will, we think, 

 be found insuperable. The shape which the pupil of the eye may 

 assume is a character which is practically of little use, since, with 

 regard to various species, we have no evidence on the subject. More- 

 over the character itself, if it could always be ascertained, appears to 

 be a rather trivial one, since amongst the Cats, which undoubtedly 

 form one genus, it may be either linear or oblong, or round, according 

 to the species *. 



As the result of our studies, we offer the following list (p. vi) of what 

 we deem probable species ; although, as in some cases, we have been 

 able to examine only a few specimens of one kind, it may well happen 

 that some forms we have treated as species may ultimately prove to 

 be but well-marked varieties. 



Indeed, so great is the variability of many of these animals that in 

 some instances whether a form is to be reckoned as a species or a 

 variety can only be matter of individual opinion. Our own tendency 

 is rather to unite doubtful forms than to separate them as distinct kinds. 

 Nevertheless we willingly adopt, provisionally, even a mere difference 

 of hue, if there appears to be any good reason for thinking it may be a 

 constant difference. We shall also rank as distinct, any two forms which 

 exhibit definite and peculiar markings of diverse kinds, even though 

 there may be individuals in which the markings are so indistinct that 

 they can only doubtfully be referred to either. Such may not be truly 

 " transitional forms," but only individuals with the characters of their 

 kind very imperfectly developed. We do not ourselves doubt that 

 * See the Proceedings of the Zoological Society for 1882, pp, 141 and 517. 



