56 Zoological groups of greatest interest 



number of examples selected from all the degrees of the zoolo- 

 gical scale. 



Travellers who traverse a countiy more or less rapidly, or 

 who, at most, remain for a few months at a time in the same 

 locality, as it forms part of the plan of the new Commission to 

 do, cannot evidently, of themselves, collect all the materials 

 necessary for the comparison which we have pointed out. 

 But, besides what they can accomplish themselves, tlft mem- 

 bers of the expedition cannot fail to find most valuable aids in 

 many places. There are at present in Sweden, Norway, and 

 Denmark, many people who study either the Avhole subject of 

 zoology, or some one of its branches, scientifically, or as mere 

 amateurs, and who are forming rich collections of the produc- 

 tions of the country. Among the Snx-dish zoologists, M. 

 Nilsson, in particular, whose courtesy is equal to his know- 

 ledge, may prove very useful to the Commission, in conse- 

 quence of the unceasing eff^orts he has made for many years, 

 to collect and bring to greater completion the necessary ma- 

 terials for his Scandinavian Fauna. 



While urging the zoologists of the expedition to collect all 

 the objects they can for the purposes of comparison, which 

 will be the more satisfactory the broader the basis on which 

 it is founded, we may at the same time point out a few zoolo- 

 gical groups which appear to us to be of greatest interest in 

 this point of view. Such are the lepidoptera ; terrestrial 

 raoUusca ; lacustrine and river moUusca and fishes ; birds 

 of prey ; passerine birds, and, among these, sparrows in parti- 

 cular ; gnawers ; but, above all, the beaver, whose habits in 

 Scandinavia ought to be determined with care ;* and the 

 fur-bearing carnivora, especially those of the genus mustela. 

 These latter will possess a double interest, as they can be 

 compared with the martins, pole-cats, and ermines of North 

 America, as well as with our own. 



It is almost unnecessary to remark, that these materials 

 cannot be of full value to science, if, along \vith each animal, 

 there is not transmitted as exact an account as possible of the 

 geograpliical situation, and topographical disposition, of the lo- 

 cality in which it was taken. The season of its capture ought 



— =- . , 



* See Note B. 



