THE DISTRTBUTIOIsr OF AXIMALS 



95 



Keeping tlicse difficulties iu mind, the following estimates, 

 for which I am largely indebted to my friend, Mr. Henry 

 Dresser (author of a great work on the Birds of Europe), will 



be found interesting. 



Species of Birds 



Square Miles. 



Europe 



Great Britain 

 Dorset 



3,850,000 



87,000 



988 



Number of Species. 



770 

 410 

 2101 



Mansel-Pleydell's Birds of Dorset. 



The numbers for Dorset are obtained by omitting all the 

 " stragglers " and very rare visitors, including all that are 

 regular immigrants or birds of passage, as well as those which, 

 though irregular, are tolerably frequent visitors. Here, again, 

 we see that a county area has rather more than half the 

 British species, as was the case wdth flowering plants and 

 some of the most extensive orders of insects. 



The difficulty of obtaining really comparable figures for the 

 countries and regions shown on page 96 is at present insuper- 

 able, but the approximations given are of considerable interest. 



The same table exhibits several points of interest, espe- 

 cially as regards the correspondence of the proportionate 

 numbers of such different organisms as birds and plants. As 

 regards the Palsearctic and N^earctic regions (temperate 

 Europe and Asia on the one hand, temperate North Am.erica 

 on the other), we see that the birds of the former are about 

 one and a half times those of the latter, the areas being nearly 

 as two to one. The plants are probably not far from the 

 same proportion; for if we take those of Europe with North 

 Africa at 10,000, and add thereto those of the Flora Orientalis 

 of Boissier (12,000), and the China flora of Hemsley (9000), 

 and allowing that the species common to any two of these may 



