12 MUSEUM OF COMPARATIVE ZOOLOGY. [Mar. 



limit my remarks, are areas tenanted by distinct faunae, charac- 

 terized by representative species which exclude one another in 

 their geographical distribution. However, the knowledge of 

 the range of these representative species will only give us the 

 means of ascertaining the true boundaries of natural faunae, and 

 is not sufficient to fill the picture of a fauna with all its belong- 

 ings. This can only be done by a special study within the 

 limits of the fauna, after these limits have once been settled. 

 In their natural association with one another, upon the surface 

 of the earth, animals bear very different relations. There are 

 those which range over the most extensive tracts of land, 

 neither coinciding with the natural boundaries of a zoological 

 realm, nor in any way marking the limits of a fauna ; as, for 

 example, the American Panther, (Felis concolor^) which is 

 found east of the Rocky Mountains, from Canada to the 

 southernmost extremity of South America. Others, such as 

 the Moose and the Reindeer, characterize climatic zones, with- 

 out defining faunae. Others coincide with peculiar physical 

 features without marking faunae, such as the animals of the 

 deserts of Africa, &c, and yet all these animals contribute to give 

 a definite aspect to the fauna over which they range ; but they 

 will not help us to determine the boundaries of the fauna, even 

 if we were to trace with the utmost accuracy their special 

 distribution. It will thus appear that the study of a fauna 

 requires specific investigations, made with a clear understand- 

 ing of what should be aimed at in order to make the science of 

 the geographical distribution of animals all that it ought to be 

 hereafter. 



The work done in that direction, in the Museum, has already 

 extended to comparisons between the faunae of the present age 

 and those characteristic of earlier periods, through all the 

 geological ages, chiefly with the view of ascertaining whether 

 there is any probability of tracing a genetic connection between 

 the animals of successive geological periods, or between those 

 of different geographical areas, and how far geographical 

 distribution and specific distinction are primary facts in the 

 plan of creation. It must be obvious that the question of the 

 origin of species is not likely to be discussed successfully 

 before the laws of the geographical distribution of organized 

 beings have been satisfactorily ascertained. 



