GROWTH OF IDEAS 287 



on the Theory of Evohition (one part in 1878, a 

 second in 1879, and a new and enlarged edition in 

 1902). . As a matter of fact, we find him in these 

 years occupied with a small but particularly 

 well-lit field of his whole work. It was not 

 merely that in a few years he buried himself in 

 the primitive forests of Ceylon, in order to pursue 

 his special studies far removed from all civilisation 

 for months together. Just at this date appeared 

 the great monograph on the medusae, which he 

 had at length concluded. The first volume {The 

 System of the Mediisce, with 40 coloured plates) 

 was published in 1879, and the second (The 

 Deei^-sea Meditsce of the Challenger Expedition 

 and the Organisms of the Medusce^ with 32 plates) 

 in 1881. And while these splendid volumes 

 showed his academic colleagues that he had no 

 mind to remain entirely on the outer battlements 

 as a philosophic champion, he plunged up to the 

 ears in a new special study of a range that would 

 have made even the most enthusiastic specialist 

 recoil. 



From December, 1872, to May, 1876, the Enghsh 

 had conducted a peaceful enterprise that will be 

 for ever memorable. A staff of distinguished 

 naturalists had gone on the ship Challenger to 

 explore the depth, temperature, and bottom of 

 remote seas. With the aid of the best appliances 

 specimens of the mud from the floor of the ocean 

 (sometimes more than a mile in depth) were 

 brought up at 354 different spots. It was known 

 from earlier deep-sea explorations that this slime 



