GEOLOGY. 315 



must we not admit in the conditions of that great problem, the maintenance 

 of animal and intellectual existence and happiness?" In other words, we 

 are in possession of but one or two facts out of a great many, and know, so 

 far, very little about the matter. 



FORMER CONNECTION OF AUSTRALIA, NEW GUINEA, AND THE 



ARU ISLANDS. 



Mr. A. R. "Wallace, in a paper on the Aru Islands, a group one hundred 

 and fifty miles South of Western New Guinea (Ann. and Mag. Nat. Hist., 

 xx, Jan. 18-58, p. 473), shows that the zoology of the islands is closely re- 

 lated to that of New Guinea and Australia; and that shallow seas not only 

 connect the two last, as others had before stated, but that they extend and 

 include the Aru group. The depth of water over the whole to Australia is 

 very nearly uniform at about thirty to forty fathoms. Mr. Wallace says: 



" But there is another circumstance still more strongly proving this con- 

 nection : the great Island of Aru, eighty miles in length from north to south, 

 is traversed by three winding channels of such uniform width and depth, 

 though passing through an irregular, undulating, rocky country, that they 

 seem portions of true rivers, though now occupied by salt water, and open 

 at each end to the entrance of the tides. The phenomenon is unique, and we 

 can account for their formation in no other way than by supposing them to 

 have been once true rivers, having their source in the mountains of New 

 Guinea, and reduced to their present condition by the subsidence of the 

 intervening land." 



Nearly one-half of the Passerine birds of New Guinea hitherto described 

 are contained in the author's collections made in Aru, and a number also of 

 species in the other tribes. 



The author farther observes, on the absence of the peculiar East Indian 

 types : "In the Peninsula of Malacca, Sumatra, Java, Borneo and the Phil- 

 ippine Islands, the following families are abundant in species and in individ- 

 uals. They are everywhere common birds. They are the Buceridce, Picidce, 

 BucconldoB, Trogonidce, Meropidce, EurylaimidoB ; but not one species of all 

 these families is found in Aru, nor, with two doubtful exceptions, in New 

 Guinea. The whole are also absent from Australia. To complete our view 

 of the subject, it is necessary also to consider the Mammalia, which present 

 peculiarities and deficiencies even yet more striking. Not one species found 

 in the great islands westward inhabits Aru or New Guinea. With the 

 exception only of pigs and bats, not a genus, not a family, not even an order 

 of mammals is found in common. No Quadrumana, no Sciuridae, no Carniv- 

 ora, Rodentia, or Ungulata inhabit these depopulated forests. With the two 

 exceptions above mentioned, all the Mammalia are Marsupials ; while in the 

 great western islands there is not a single marsupial! A kangaroo inhabits 

 Ani (and several New Guinea), and this, with three or four species of Cuscus, 

 two or three little rat-like marsupials, a wild pig and several bats, are all the 

 mammalia I have been able to obtain or hear of." 



ON THE PROBABLE ORIGIN OF THE ORGANIZED BEINGS NOW LIV- 

 ING ON THE AZORES, MADEIRA, AND THE CANARIES. 



The following letter, on the above subject, has been addressed by Oswald 

 Heer to M. de Candolle : 

 In your Geography of Plants you have adopted the opinion of Edward 



