The Scottish Naturalist. 45 



College, Mr. Thomson applied for the Cork professorship, and 

 was successful. A few years later on Dr. Dickie's vacating the 

 same chair in Belfast University, on his return to Aberdeen as 

 Professor of Botany, Dr. Thomson was a second time his suc- 

 cessor. This latter appointment he held from i860 until in 1870 

 he succeeded Dr. Allman as Professor of Natural History in the 

 University of Edinburgh. Owing to the state of his health, he 

 resigned his office in October, 1881. 



From an early period he directed his attention to marine 

 zoology. He first appears as writer on zoology in a short paper 

 in the Amials a?id Magazine of Natural History, in 1852, entitled 

 " Notes 071 some Scotch Zoophytes and Polyzoa ; " and much of his 

 later work bears on these and allied groups of marine animals, 

 both recent and fossil. The embryogeny of the Echinodermata 

 interested him greatly, and he worked out the life-history of several 

 forms very fully, and made several interesting and important dis- 

 coveries in this way in the relationships of the various living and 

 fossil forms. 



His scientific studies led to his becoming always more con- 

 vinced of the probable abundance and diversity of the fauna to be 

 found by systematic dredging of the deeper parts of the ocean 

 bed, where it has been supposed that life could not exist. Be- 

 lieving it to be of great importance in the advancement of know- 

 ledge of recent and of fossil animals alike, he exerted all his 

 influence to obtain from the Admiralty the use of a vessel suitable 

 for such investigations, and properly equipped for a cruise. In 

 this he was successful; and in August 1868 the "Lightning" 

 sailed for a cruise in the North Atlantic. The vessel returned to 

 Oban in September. A full account of the results will be found 

 in Thomson's " Depths of the Sea." They proved the existence 

 of abundant and varied animal life at depths of 600 or 700 

 fathoms. Some of the forms met with were startlingly similar to 

 groups supposed to have died out in the Tertiary or the Chalk 

 periods ; and public interest was awakened vividly to the import- 

 ance of such investigations in their bearing on the past history of 

 the earth as interpreted by its fossils. Another subject of much 

 interest and importance in the study of marine faunas and 

 climatology had some light thrown upon it during the cruise — 

 viz., the distribution and temperature of oceanic currents. The 

 investigations were resumed next year in the " Porcupine," from 

 May till September. During part of this time Dr. Thomson 

 directed operations in the Bay of Biscay, and in the Atlantic to 

 the west of the British Islands. Again, in 1870, the "Porcupine" 

 was sent out, but an attack of illness prevented him from taking 

 part in the work. The results of both cruises are described in the 

 " Depths of the Sea." They were such as to raise still higher the 

 general expectation of great and very valuable scientific results 

 being secured were a well-equipped expedition sent forth to sur- 

 vey the bottom of the great oceans, with a scientific staff thoroughly 



