BRIEF HISTORY OF Tllli .SCIENCE OF ZOOLOGY 471 



usually new characters which breed true from their start. 

 We find ourselves thus in the twentieth century with the 

 theory of evolution generally accepted, but with the method 

 of evolution incompletely worked out. There thus remains 

 plenty of work on this theory to be done in the future. 



Zoological expeditions. — We have seen that the work of the 

 encyclopgedists led men to add to the number of known species 

 by exploring new countries. The great sj^stematic works of 

 Linneeus and the others had a similar effect. One of the 

 greatest of the early expeditions was undertaken by Pallas 

 (b. at Berhn 1741, d. 1811), who travelled through Siberia 

 and as far south as the Caspian Sea. He also investigated the 

 fauna of eastern and southern Russia in Europe, and published 

 the results of his studies in extensive books. 



During the early part of the nineteenth century a great 

 interest was revived in the study of marine animals, and 

 many expeditions were sent around the world. Of these the 

 Challenger Expedition is the most noteworthy. Its results 

 are published in fifty fine quarto volumes. In this country 

 the expedition under Wilkes, which opened Japan to Western 

 civilization, and those of Alexander Agassiz in the Blake 

 and the Albatross are the most noteworthy. Despite all of 

 this activity, much of the land and of the sea remains to be 

 explored. 



