ON BIOLOGY. 33 



first mentioned we find many characteristic small mam- 

 mals not found on the African Continent, while it lacks 

 all the large carnivora, the apes, giraffes, elephants, ante- 

 lopes and others which are found there. Wallace has said: 



"The African Continent is preeminently the country of 

 large mammalia. It possesses an abundance of elephants, 

 rhinoceroses of several species, giraffes (now peculiar to 

 it), gorillas and baboons the largest of the ape tribe a 

 host of large and remarkable antelopes, the huge hip- 

 popotamus, several species of zebras, wild buffaloes, sev- 

 eral remarkable forms of swine, and an abundance of 

 lions, leopards, and hyenas forming together an assem- 

 blage of large and highly organized animals such as occur 

 nowhere else upon the globe. There are also many 

 smaller, but very remarkable forms." 



And so it goes with the four remaining regions defined 

 above, the Oriental, the Australian, the Neotropical, and 

 the Nearctic. Each possesses its peculiar and character- 

 istic forms of mammals, and each region its varying 

 physical aspect. What has been said of the first two 

 holds true in principle in all the others. 



Australia of the Australian Region is especially charac- 

 terized, inasmuch as all the more ordinary forms of mam- 

 mals are not found there, their room being taken by the 

 varied group of the marsupials, of which there are 5 

 distinct families and many genera. Echidna and Orni- 

 thorhynchus, two other distinct families of most remark- 

 able mammals, are also found on the Australian Conti- 

 nent. 



Thus we see how it is that animal and plant life is dis- 

 tributed over the face of the globe according to certain 

 natural laws, and that those distributions have varied 

 during the past history of the earth, owing to the varied 

 application of the same laws and to other circumstances. 

 In short there is in the individual case of any existing 

 animal or plant on the earth a reason for its being found 

 over one area and not over another. There is a very good 

 reason why giraffes are found in Africa and not in Mex- 

 ico, as there is why we find yucca in the heart of Mexico, 

 and not in Africa. 



Science has made very considerable progress toward 

 the elucidation and demonstration of many of the laws to 

 which I refer; there still remains, however, in the grasp 

 of the great unknown a vast store of tacts not yet brought 

 to light, though the incessant investigation of the scien- 

 tific researcher tends to almost daily pass them over to 

 the realm of the known. 



