40 FOUNDERS OF OCEANOGRAPHY 



It was during this period of teaching at Belfast that he 

 began to make his mark in the scientific world as a marine 

 biologist who studied animals both living and extinct, and 

 published his investigations on British Coelenterates and 

 Polyzoa and on fossil Cirripedes and Trilobites. In working 

 at Palaeontology he became interested in fossil Crinoids, and 

 so was led to the investigation of their only living representa- 

 tives in our seas — the Rosy Feather Stars — a study which, 

 we shall see, led him step by step to the great climax of his 

 career, the leadership of the " Challenger " expedition. In 

 1862 Thomson completed his well-known memoir, " On the 

 Embryogeny of Antedon rosaceus " (published in the Philo- 

 sophical Transactions of the Royal Society for 1865), illustrated 

 by a beautiful series of drawings representing the develop- 

 ment and structure of the " pentacrinoid " stages in the life- 

 history of the young Antedon. 



It was at this time, also, that he became interested in 

 those questions concerning life in the great depths of the 

 ocean, the elucidation of which was to be his life-work and 

 make him famous. It will be remembered that Edward 

 Forbes, from his observations in the Mediterranean (an 

 abnormal sea in some respects), regarded depths of over 

 300 fathoms as an azoic zone. It was the work of Wyville 

 Thomson and his colleagues on various successive dredging 

 expeditions to prove conclusively, what was beginning to be 

 suspected by naturalists, that there is no azoic zone in the 

 sea, but that abundant life belonging to many groups of 

 animals extends down to the greatest known depths of from 

 four to five thousand fathoms — nearly six statute miles from 

 the surface. We can trace the gradual growth of Thomson's 

 ideas in regard to the sea with the natural widening of his 

 scope — from collecting as a student on the shores of the Firth 

 of Forth to dredging as a young professor along the coasts of 

 Ireland, and then to the successive deep-water expeditions 

 in the surveying vessels " Lightning " and " Porcupine," 

 and finally to the great world-wide exploring voyage of the 



