39 



plainly that the fauna of a sea bottom was not materially af- 

 fected by mere difference of locality, but was regulated by 

 similarity of temperature. The cold water similar to that of 

 the Arctic Seas prevailed at these great depths, and in fact 

 this might be alleged regarding about three-fifths of the earth's 

 entire surface. Therefore, where this low temperature existed, 

 which it did over a vast region, the same form of life prevailed. 

 Bands of temperature in the ocean and bands of fauna were cor- 

 spondent. The more southerly investigations were proceeded 

 with the deeper down were the coral forms found. This state- 

 ment, of course, does not embrace those portions which are af" 

 fected by warm equatorial currents, notably by the Gulf Stream. 

 When the dredge touched on that region below, influenced by 

 the Gulf Stream, the fact was immediately recognisable by the 

 great difference in the forms brought up in the dredge. But, 

 as regards Arctic forms, let it be understood that even off the 

 coast of England such can be found, if we go to the proper 

 depth. The relations which many of the forms discovered 

 sustained to the Tertiary fossils of Sicily, and to fossils found 

 in old formations, were spoken of; and, in connection with 

 existing species, it was mentioned that many species had been 

 dredged in the northern seas similar to, but not quite identical 

 with those found in Australian and southern seas. Many 

 species, altogether unknown before to scientific men, had now 

 been discovered in these great depths, especially in the sponge 

 family, whose headquarters seemed to be in the abysses of 

 ocean. In fact, as regards sponges, these recent dredgings 

 had been accumulating new forms so rapidly that the lecturer 

 believed we were not yet in a position to attempt any classifi- 

 cation of them. Dr. Thomson then described minutely, and 

 exhibited some most beautiful specimens of deep sea sponges, 

 sea urchins, starfishes, and crinoids, captured during his last 

 cruise in the summer of 1870. 



