466 ZOOLOGY 



certain species are extremely variable ; but on closer 

 examination this seems to be illusory. There are, in 

 fact, very numerous allied species, each occupying its 

 own area and uniform within it. * 



special 5. Certain parts of t^he tropics are famous for the 



abundance of particular groups of creatures, as all 

 collectors know. Thus for snails we go especially to 

 the Philippine Islands, the Hawaiian Islands, Cuba, 

 or Jamaica ; for ferns, to Jamaica. Butterflies are ex- 

 cessively numerous in South America. If we care for 

 rats, the Malay Archipelago will supply almost un- 

 limited numbers of species. In general, continental 

 areas are much richer in species than are islands, if 

 we except certain groups. There is no part of the 

 tropics which will not reward an industrious collector 

 with numerous novelties, and many generations of men 

 must pass before the biota of the richest regions of the 

 world is adequately catalogued. The best treatment 

 of a single tropical area is found in the series of volumes 

 on the Fauna of British India, published by the British 

 Government, but this is still very incomplete. The 

 Biologia Centr all- Americana is a great work on the 

 animals and plants of Mexico and Central America, 

 a splendid contribution to science, but very costly, and 

 enumerating only a fraction of the life really existing 

 there. 



References 



WALLACE, A. R. The Malay Archipelago. 



RODWAY, JAMES. In the Guiana Forest. Second Edition, 1912. 

 ROOSEVELT,. THEODORE. Through the Brazilian Wilderness. 1914. 

 SPRUCE, RICHARD. Notes of a Botanist on the Amazon and Andes. 1908. 



