294 Dr. J. H. Blasius on the Diversity in t/ie Estimate 



On the side of the majority stands, besides all other ornitho- 

 logists, Brehm's * Lehrbuch,' published in 1823 ; on the other 

 side stands Brehm alone, in the ' Naumannia ' and the ' Vogel- 

 fang' of the year 1855. So far as any conflict of principles is 

 in question, therefore, we have to do with a struggle between 

 the entire science of ornithology up to the present time, and the 

 most recent views of Brehm. The contradictions depend essen- 

 tially, although not entirely, upon this conflict of principles. 



The previous estimate of the European Ornis falls into two 

 series of very different values — the species regularly inhabiting 

 Europe, and those accidentally visiting that continent. The 

 species not regularly belonging to Europe require merely a sort 

 of police-notice, or domiciliation — we have simply to do with 

 the question whether we shall give a place in our books and 

 catalogues to the exotic species which may wander into Europe, 

 or pass them by unnoticed. If they be left unnoticed, the ques- 

 tion as to the estimation of the European Ornis becomes greatly 

 simplified. 



If, as is almost universally the case, the stray immigrants arc 

 to be noticed, their acceptance depends simply on the proof of 

 their voluntary appearance in Europe, without importation. 

 Imported birds, or exotic birds escaped from confinement, have 

 no right to a place in our Ornis. The occurrence oi Spiza ciris, 

 L., in England, of Parra jacana, L., in the south of France, of 

 Nycterodius violaceus,L.,\n England, oi Pledropterus gambensis in 

 France, of Erismatura ferruginea, Eyton, in Belgium, of Halieus 

 sulcirostris, Brdt., and of many birds commonly kept in aviaries, 

 may remain unnoticed without the least objection. 



The number of voluntary immigrants, the occurrence of which 

 in Europe is positively ascertained, amounts at the present mo- 

 ment to a little over 100 species. It has become greater nearly 

 every year, and may be expected to continue increasing. 



These species are distributed as follows, according to their 

 native countries and the various natural orders : — 



