~6 On the -present state of Zoology. 



ing to connect the more extreme cases, and thus clearly proving- all 

 to be of one species. 



From experiencing the great difficulty which attends the exact dis- 

 crimination between species and vaiueties, especially in certain groups 

 in which variation of character is very frequent, some have imagined 

 that there was nothing definite or constant in species themselves, but 

 that they passed insensibly into one another. To this opinion, al- 

 though embraced by many eminent naturalists, we are strongly op- 

 posed. It may be true that hitherto no definition of a species has 

 been brought forwards which will meet all cases ; but until our means 

 of observation shall have been more extended than they have at pre- 

 sent, this simply proves the imperfect state of our knowledge on this 

 subject. For let us consider how much is wanted to enable us to fix 

 such a definition with certainty. It has been observed with reference 

 to this point, that " we ought to see species in all their several loca- 

 lities from north to south ; to get together all the varieties of age, 

 form, colour, and size, in order to construct from all these modifica- 

 tions a table representing one well-known species, and to establish as 

 many of these tables as there are true species of organized beings. 

 By these means we should probably arrive at some law which would 

 fix the limits of the species in its modifications, and serve consequent- 

 ly as the basis of an exact definition."* 



Having brought our remarks to this point, we shall simply, before 

 concluding, say a few words for the direction of those, who may be 

 entering on the branch of science we are here considering. We have 

 more than once alluded to the immense field which Zoology brings 

 before us. We have also noticed the great partiality shown by na- 

 turalists towards certain parts of that field in preference to others. 

 Now what we would recommend to such as really desire to advance 

 its progress, — is, — that they restrict their chief attention to some given 

 department, and, when practicable, to those particular groups which 

 have been least studied. It is utterly out of our 'power to become 

 acquainted with all the existing species of nature. The longest life, 

 added to the enjoyment of the most favourable opportunities, will not 

 suffice for acquiring more than a very limited knowledge of the de- 

 tails of their history. It must, then, be by division of labour, that 

 we try to perfect the science, so far as human researches can perfect 

 it. We must bring our observation to bear on those parts of it which 

 are behind the others, — we must apportion such parts amongst us ac- 

 cording to the respective circumstances in which we are placed, and 



* Lam. Hist. Nat. des An. sans Vert. (2d edit.) torn. i. p. 166 Note by the 



Editors. 



