PART III. 



TABLE OF DISTRIBUTION. 



In preparing the table of distrilxition it has been necessary, in order to 

 keep it in convenient form, to limit the number of localities included. Thus, 

 the Philippines have been taken together, even though conditions vary greatly 

 upon the different islands. Again, species have been described which are appar- 

 ently confined to son\e small islet, and in these cases they have been credited 

 to the nearest listed locality to which they belong faunally or geographically. 

 For instance, Dasia aignanum (Boulenger) was described from St. Aignan's 

 Island in the Louisiade Archipelago ; but this species has been credited to British 

 New Guinea, a region of which the Louisiade Archipelago forms simply a dis- 

 jointed part, and to which the group belongs both zoologically and geographically. 



For the table see p. 169-203. 



ZOOGEOGRAPHY. 



The conditions which limit an attempt to use the data of the geographic 

 distribution of animals as an aid in reconstructing past geographic changes in 

 the East Indies are very many. In the first place, an accurate, systematic 

 knowledge of the fauna of any one East Indian Island is still far from an accom- 

 plished fact. Of many islands we know nothing at all. We may wish to argue 

 from what we know of the Amphibia of one island, and to compare this with 

 the conditions on another island where the birds are well known, liut the amphi- 

 bians little, or not at all. .Vgain, we know that species often become extinct, 

 especially upon islands, for no apparent reason; so that we may be constrained 

 to argue from the absence of certain forms, and yet never feel sure that they 

 have not existed in the past. 



Conditions of life on islands, as elsewhere, are subject to certain purely 

 economic conditions: beasts of prey demand the presence of a definite number 

 of plant-eating animals, the latter demand the proper food supply of plants. 

 Insectivorous animals must have insects; and insects must have appropriate 

 plants, each in definite supply. Thus a certain balance must always be main- 

 tained; and this may be accomplished at times only by the dying out of some of 



