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Classification of Animals. 17 



At the present day, though the origins of many of the 

 great branches seem more uncertain than ever, some of 

 the minor ramifications are being worked out with what 

 seems strong probability of accuracy. In course of 

 time it may be possible to piece the smaller branches 

 together after the fashion of a puzzle picture. 



Before the work of Ray, the term "species" was used 

 quite loosely, as it still is by the careless conversation- 

 alist who speaks indifferently of "the fish Gradesof 

 species" or "the human species". Accord- ciassifica- 

 ing to Ray, however, all similar individuals * 

 which exhibited constant characters from generation to 

 generation form a species, and should be called by a 

 particular name. Thus there is in Britain one species 

 of daisy, but there are several species of buttercups. 

 At the same time, Ray observed that the two sexes of 

 the same species might be very different, and that one 

 species of plant might "degenerate" into another. 



Linnaeus defined species as Ray had done, but even 

 more rigidly. Each species was descended, he said, 

 from an originally created pair, and each expressed an 

 idea in the divine mind. Moreover, these ideas were 

 consecutive, each species being intermediate between 

 two others in the great system of nature, wherein, as 

 Leibnitz had insisted, there was no leap or hiatus. Thus 

 two long-lived dogmas were formulated: (a) the fixity 

 of species, and (b) the doctrine of continuity natura 

 non facit saltum. At present no naturalist accepts the 

 first, and many are very doubtful about the second. 



To each species, as we have already noted, Linnaeus 

 gave a double name ; thus the lion was called Felts leo 

 and the daisy Bellis perennis, the second name being 

 the specific title, while the first name was that of the 

 genus a group of more or less similar species. Simi- 

 larly, Linnaeus grouped genera into orders, and orders 



to classes. 



No great change has been made in the grades of 

 :lassification. In 1780 Batsch introduced the useful 

 grade "family" between the order and the genus; 

 Haeckel introduced (1866) the term "phylum" for any 

 distinct branch of the genealogical tree, whether it in- 



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