REPORT ON ZOOLOGY. 247 



less SO to determine the parts of the system to which these links 

 belong. But of these two, there can be no doubt the latter is 

 what we stand most in need of. I question whether we shall not 

 be rendering more service to zoology by paying closer attention 

 to the species we are already acquainted with, than by further 

 augmenting the immense collection of uninvestigated forms 

 which exists now in our cabinets. We have, perhaps, sufficient 

 materials on our hands, though not for discovering the whole 

 natural system, at least for solving many important problems in 

 zoology, were we only better instructed in the natiu-e of these 

 materials. It has been shown in the course of this Report, that 

 there are large groups, even whole classes, of which the true 

 situation and affinities are either not determined at all, or in- 

 volved in much uncertainty, from the impei-fect knowledge we 

 have of their structure and oeconomy ; and in the details of the 

 system, there is not one class which does not present many 

 genera, and a vast many more species in this predicament. 

 Here then is where the researches of naturalists should be di- 

 rected. Until we shall have more closely analyzed the charac- 

 ters of these groups, and learnt both the method of variation and 

 relative importance of all the organs, until we shall come to 

 understand their whole structure as compared with those struc- 

 tures we are already acquainted with, we can neither determine 

 the affinities of these groups, nor of any others allied to them 

 which we may hereafter discover. 



Researches of the above nature are, perhaps, best embodied 

 in monographs. The value of such works has been every day 

 more and more appreciated since the science has become so 

 extensive, and since its legitimate object has been better under- 

 stood, especially when they refer to every point in the history 

 of the group treated of, and when due care is taken first to 

 ascertain what others have written on the same subject *. Many 

 excellent monographs fulfilling these conditions already exist, 

 some of which have been alluded to, and others might have 

 been had it been allowable to enter so much into the details of 

 the subject. Nevertheless it would be extremely desirable to 

 have them multiplied. By the help of such works we may 

 arrive step by step towards a more complete generalization of 

 the large number of facts embraced by zoology, at the same time 

 that we greatly facilitate the researches of other naturalists. But 

 all inquiries into the structure and oeconomy of animals presup- 

 pose an exact discrimination of species. Without this the most 

 detailed observations are rendered of little use, and it is the 



t Seethe article Monographie, by Dccandolle, in the Diet, des Set. Nat. 



