49° 



PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



ing. Islands are of two kinds — continental islands and 

 oceanic islands. Continental islands are outliers of con- 

 tinents, separated from them only by subsidence. They 

 have a geological structure similar to the mother conti- 

 nent. Oceanic islands are those which have no connec- 

 tion with any continent, but have been built up from the 

 ocean bed by volcanic eruption in comparatively recent 

 geological times. The fauna of continental islands is 

 always related to that of the mother continent, differing 

 from it in proportion to the width of ocean separating 

 and the time of separation. The fauna of oceanic is- 

 lands have no such evident relation to any continent. 

 As examples of the former group we have Ceylon, Java, 

 Borneo, Sumatra, Japan, etc., as appendages of Asia; 

 Madagascar, of Africa ; the British Isles, of Europe ; the 

 West Indies, of North America, etc. Of oceanic islands 

 we have as examples the Bermudas and Azores in the 

 Atlantic, and all the Polynesian Islands in the Pacific. 



4. Madagascar. — We have already seen that the 

 mammals of Madagascar differ greatly from those of 

 any other country, but that their nearest alliance is with 

 those of Africa. We now add that this alliance, how- 

 ever, is only with those we called the indigenes, and not 

 at all with the invaders. 



Explanation. — In preglacial times, when Africa was 

 isolated from the rest of the world, Madagascar was 

 connected with it, and both were inhabited by the in- 

 digenes. Before the glacial epoch, and therefore before 

 the invasion of Pliocene mammals, Madagascar was sep- 

 arated from the continent by subsidence, and these iso- 

 lated indigenes were spared the invasion and conflict. 

 Since that time divergence has gone on until now the 

 fauna is very peculiar. In the fauna of Madagascar we 

 probably have a nearer approach to the original inhab- 

 itants of both than we now have in the African indige- 



