344 GEOGRAPHICAL DISTRIBUTION 



of several species of different genera from, say, a locality in the 

 north varied in the same way from examples of a set of the same 

 species from the south, and so with eastern and western examples. 

 In principle this was not novel or unexpected. Indeed it had been 

 noticed in some instances in Europe, particularly, as the "WTiter can 

 testify, by the late Mr. Gould many years ago ; but the small size 

 of our own quarter of the globe compared with that of North 

 America, and still more the short series of specimens which existed 

 even in the largest of our collections, forbade the generalizations 

 that at once became possible and almost suggested themselves 

 when the vast aggregations obtained by Baird and the elder 

 Agassiz were studied and compared. In the meanwhile, however, 

 European, and especially English, ornithologists had been growing 

 dissatisfied with the shortcomings of their collections, and took 

 pains to enlarge them, but there were special difficulties in the way 

 of obtaining specimens from the eastern portion of the Palsearctic 

 area, and Central Asia was practically an unknown country. That 

 their efforts were more or less successful may be seen by Mr. 

 Dresser's Birds, of Europe, the publication of which marked an 

 enormous forward stride, but still the dearth of sufficient series of 

 specimens from Eastern Europe, and particularly from the Asiatic 

 portion of the Eussian Empire, continues to be keenly felt. The 

 zeal shewn by Mr. Seebohm to meet this want deserves high 

 commendation, and of late Russian ornithologists have turned their 

 attention to the question of local races. The immediate effect has 

 been no little confusion, but that is unavoidable, and none can 

 doubt that much of it will disappear, so that we may hope our 

 knowledge of the ornithology of the Palaearctic area will in a few 

 years be on a level with that which Americans possess as regards 

 the Nearctic. But a word of warning may be uttered in respect of 

 both. Many writers on natural history find it hard to realize the 

 fact, undeniable according to the principles of the doctrine of 

 Evolution, that if all the individuals of any genus that ever existed 

 could be set before a naturalist, he would be unable, even though 

 gifted with the most critical eye, to separate them into species, for, 

 however unlike the extremes might be, the means would shew an 

 unbroken series between them. It must be obvious that these 

 intermediate individuals are the ancestral, generalized forms, while 

 the rest shew a greater and greater tendency to specialization in 

 one way or another. In the course of ages many of these inter- 

 mediate forms disappear, and then it is right to regard those that 

 survive without near relations as good species. But others there 

 may or will be that, however they may vary locally, are still un- 

 mistakably linked. The forms that connect them continue the 

 nearest heirs of the ancestral stock, and present its more general- 

 ized features. Thus to assume, as some do, that these connecting 



