JASrtJAEY 1, 1897.] 



SCIENCE. 



27 



ttat of the extinct ancestors of existing faunas 

 — and has brought together a multitude of sig- 

 nificant facts which no one but a paleontologist 

 could safely venture to attack. The result is a 

 volume which, in spite of the imperfections and 

 errors incident to so great an undertaking, will 

 rank among the standard works on Geographic 

 Distribution for many years to come. 



The influence of man on the dispersion of an- 

 imals is excellently told. Mr. Lydekker says : 

 ' ' Probably ever since man has existed in any 

 numbers on the globe he has been exerting a 

 more or less strongly-marked influence on the 

 distribution of animals, either by destroying 

 them or by conveying them to countries or dis- 

 tricts which are not their natural home. By the 

 involuntary aid of man the common rat and 

 mouse, which belong to a genus unknown in the 

 New World, have been conveyed to every coun- 

 try in the globe ; while the rabbit has been car- 

 ried to the antipodes, where it has flourished 

 and increased in an unprecedented manner. 

 Cattle and horses have been introduced into 

 South America, Australia and other countries 

 where they were naturally unknown, and by 

 their rapid increase have shown that the ab- 

 sence of particular animals from particular dis- 

 tricts is not necessarily due to their being un- 

 suited to live there, but rather to the fact that 

 they have been unable to find their way thither. 

 The fallow-deer, again, has been imported from 

 its Mediterranean home into England and other 

 countries of northern Europe ; while goats and 

 pigs have been carried to a number of oceanic 

 islands, where they have done irreparable harm 

 in exterminating the native fauna and flora. ' ' 

 Sheep also might have been mentioned among 

 the potent destroyers of native floras. "In all 

 these instances," Mr. Lydekker continues, "the 

 fact of the introduction has always been more 

 or less clearly known, and therefore no diffi- 

 culty arises as to what are native and what are 

 introduced forms. Very different, however, is 

 the case with the Islands of the Malay Archi- 

 pelago, where the natives, who have a wonder- 

 ful facility for taming animals, have carried a 

 species peculiar to one district or island to local- 

 ites where it is quite unknown as a native ; and 

 in consequence of this transportation and accli- 

 matisation it is probable that several mammals 



have been given a habitat to which they have 

 not the most remote right. To the Malays is 

 due the introduction of the small civet known 

 as the rasse into Madagascar. Whether the 

 dingo, or native dog of Australia, was intro- 

 duced at an exceedingly remote era by the 

 original colonizers of that island, or whether it 

 is truly indigenous, is a question that will prob- 

 ably never be decisively answered. It is like- 

 wise quite impossible to say what part man may 

 have played in the extermination of the large 

 mammals that inhabited Europe about the close 

 of the glacial period, but it seems quite probable 

 that he may have had a considerable share in 

 their destruction. Be this as it may, the do- 

 mestication of certain mammals, has undoubt- 

 edly had the effect of destroying the wild race, 

 as is remarkably exemplified by the two exist- 

 ing species of camel, of neither of which do we 

 know the original habitat. " (pp. 16-17.) 



In treating of barriers to dispersion Mr. 

 Lydekker revives the fallacy that ' ' high moun- 

 tain ranges form an effectual barrier to the mi- 

 gration of mammals, ' ' but he cites no examples. 

 It is true that in many instances, as in the 

 Himalaya, mammals inhabiting the lands on 

 opposite sides of the mountains are widely dif- 

 ferent. But this is due to a radical difference 

 in the climates or physical features of the 

 countries themselves, and not to the presence 

 of the intervening mountains. Does any one 

 know of the existence of a mountain range in 

 the whole world which is continuously high 

 enough and long enough to keep mammals 

 from crossing it or passing around it if the 

 country on both sides is suitable to their needs ? 

 Mountains are barriers to distribution only so 

 far as their own mass is concerned. 



While expressing his general adherence to 

 the view that after mechanical barriers, such as 

 oceans, temperature is the chief factor in fixing 

 the limits beyond which species and genera do 

 not pass, he cites as exceptions the time-worn 

 cases of the puma and tiger, using these names 

 in the sense of species. He says : ' ' There are 

 several species, more especially among the car- 

 nivorous mammals, which seem quite indepen- 

 dent of both station and temperature, the New 

 World puma ranging from Patagonia to Canada, 

 while the tiger inhabits alike the burning jun- 



