96 



THE ZOOLOGIST. 



supposed that the head of the Vulture was made naked for the 

 purpose of feeding on putrid flesh, yet the head of the clean- 

 feeding Turkey is similarly naked. It might be held that the tail 

 of the tadpole was given to it for swimming, yet the tadpoles of 

 the Surinam Toads, which never enter the water, have a similar 

 tail. 



In treating of instinct he has to make remarkable ad- 

 missions with regard to the slave-making ants. He accounts 

 for the habits of the Cuckoo also by Natural Selection. The 

 American Cuckoo builds a nest and sits on its eggs. Suppose 

 that at one time the European Cuckoo had the same habit, but 

 that occasionally it laid an egg in another bird's nest. If the old 

 bird profited by this means and was enabled to migrate earlier, 

 or the young birds were made more vigorous, then the old birds 

 or young would gain an advantage. The young would be apt to 

 follow by inheritance the habit of the parent, and lay eggs in 

 other birds' nests, and so on by degrees until we have the present 

 condition. This habit of laying eggs in other birds' nests is seen 

 in the case of the Guinea-fowl depositing eggs in Partridges' 

 nests, and Pheasants and Greyhens in each other's nests. 



The want of evidence in ancient times of the fossil connecting 

 links between Darwin's original species and their present de- 

 scendants he lays solely at the door of the imperfection of the 

 geological records. He affirms that it is only during subsidence 

 of the sea-bottom that our great geological deposits rich in 

 fossils have been formed. Moreover, he points out that we 

 would not expect to find the missing links intermediate between 

 any two given species, but between each and a common pro- 

 genitor, e. g. the Pouter and Fantail are both derived from the 

 Eock-Pigeon ; if all the intermediate varieties existed there 

 would be a close series between each and the Rock-Pigeon, but 

 none intermediate between the Pouter and Fantail. 



He shows how little of the surface of the world has been 

 minutely explored for fossils, and how closely consecutive forma- 

 tions are related to each other in their fossil remains as com- 

 pared with the formations more distant from each other in 

 time. One of his supporters, in criticising Agassiz's views in 

 regard to prophetic types (that is, the combination in an animal 

 of structural peculiarities which at later periods are only observed 



