98 THE WORLD OF LIFE 



distances. At all events the extreme richness of Xew Guinea 

 in both birds and plants, and not improbably in insects also, 

 is a matter of very great interest.^ 



Having shown by the best statistics available that the general 

 phenomena of the numerical distribution of species over small 

 or large areas correspond in their main features for such 

 diverse groups of organisms as plants, insects, and birds, it 

 is quite needless — even if it were possible — to attempt a 

 similar enumeration for other groups. In reality, with the 

 one exception of land-shells, the materials do not exist for 

 any other organisms. Even the mammalia and reptiles have 

 never been systematically collected in tropical countries, as 

 hirds and insects have been collected, and what materials do 

 exist are more difficult to obtain. But to give the general 

 reader some notion of the extent of the whole world of life 

 as now studied by biologists, I will give a tabular statement 

 of the numbers supposed to be actually described, from the 

 estimate made by Mr. Shipley above referred to in the case 

 of insects. 



As regards these figures, I am informed by Mr. R. 

 Lydekker that he considers the Mammalia to be much exag- 

 gerated by writers who reckon slight local forms or varieties 

 as distinct species. Thus 8 species have been made of the 

 common brown bear, and 16 species of various local forms 

 of mouse-deer (Tragulus). On the other hand, although the 

 number of insects here given seems enonnous, Mr. D. Sharp, 

 a very experienced entomologist, thinks that the number ac- 

 tually existing is five times as great — that is, more than two 

 million distinct species ! 



1 Eor a full explanation of the six great Zoological Regions, here enu- 

 merated, the reader is referred to my Geographical Distribution of Animals, 

 vol. i. chap. iv. ; or for a more popular account of them to my Island Life, 

 chap. ill. 



