ORGANIC EVOLUTION 61 



duckbill is a very low form of vertebrates, being a 

 monotreme. In Australia the forms of animal life 

 found upon the discovery of the island consisted of 

 those found, also fossilized in the Cretaceous rocks 

 elsewhere. The inference is that, in the Cretaceous 

 period, Australia was connected with the continent of 

 Asia, and was then, or soon thereafter transformed 

 into a large island, but not of sufficient dimensions to 

 make geographical distribution efficient, as an element, 

 in the evolution of new species, from the lower orders 

 of vertebrates then existing. About one-third of the 

 island the interior, is a desert without animal life. 

 If Australia had remained a part of the continent of 

 Asia above, as it is below the surface of the ocean, the 

 same mammalian forms would have evolved there, as 

 in Asia. The absence of mammals, and the persistence 

 of marsupials are thus accounted for by natural cause 

 and effect. It was while on the voyage of the Beagle, 

 that Darwin noticed a similar anomaly in the fauna 

 of the Galapagos Island, six hundred miles off the 

 west coast of South America. The fauna there con- 

 sisted almost entirely of birds, with three species of 

 land tortoise, and five species of lizard, no mammals. 

 But he noticed that the forms of these were very 

 closely related to those on the mainland. The infer- 

 ence was, that the islands had been colonized by such 

 of the continental forms as could cross the intervening 

 strip of the sea, the birds by flying, the lizard, and the 

 tortoise, or their eggs transported on drift wood, or 

 carried by water direct. But why, if special creation 

 were a fact, was there an absence of such forms of the 

 animal kingdom, as could not have been brought in 

 some way from the continent? These islands are as 

 well adapted to mammal life as the continent is, and if 

 all mammals were specially created, why not here? 



