far comparison — Migrations. 57 



also to be mentioned. These circumstances, always so useful, 

 become indispensable wlien we wish to compare individuals of 

 the same species, but from different localities ; for the slighter 

 the differences we attempt to appreciate, the more complete 

 and precise ought to be the means of comparison. 



The zoologists of the expedition may likewise co-operate 

 very usefully towards the completion of the histoi'y of Euro- 

 pean spftcies, by collecting, by every means in their power, in- 

 formation regarding the migrations, whether of fishes, littoral 

 birds, or land birds of the interior of the Scandinavian penin- 

 sula, more particularly in its northern part. Many travellers, 

 especially Acerbi, according to Julin d'Uleaborg, and some 

 other modern zoologists, have already published various docu- 

 ments on these subj'ects, but many still remain to be collected. 

 It is to be desired that a list could be drawTi up, as complete 

 as possible, of all the migratory species ; and that we should 

 be able to answer the four following questions in regard to 

 each of them. 



\st. Do its migrations take place regularly every year .^ 

 2d, What is the period of its arrival ? - 



3(/, How far does it advance northward ? 

 \th. What is the date of its departure .f" 

 If, as thei'e is every reason to think, these questions cannot 

 be answered in regard to all the species, it will be at least use- 

 ful if the zoologists of the expedition attempt to give a precise 

 solution for a certain number of them, taken as examples. 

 We may point out, in particular, for their attention, the swal- 

 low and cuckoo, a bird of which it will be otherwise desirable 

 to study the manners with care, in order to see if it does not 

 differ, in this respect, from the cuckoos of central Europe, as 

 we ju:e a.ssured, but without sufficient proof, to be the case 

 with those of .Japan. 



In regard to the animals which do not migrate, it will be of 

 very great interest, at least in relation to the northern part of 

 the peninsula, to collect all the facts calculated to make us 

 understand the condition in which they pass the winter. AV'e 

 especially recommend this consideration among the higher 

 animals, in respect to the gnawers, insectivorous species, 

 badgers, and bears themselves, about which it will lie easy to 



