BY THE PEESIDENT. 181 



deep sea, when ho says that the hitter "is inhabited by a fauna 

 more rich and varied on account of the enormous extent of the 

 area, and Avith the organisms in many cases apparently even more 

 elaborately atul delicately formed, and more exquisitely beautiful 

 in their soft shades of colouring, and in the rainbow tints of their 

 wonderful phosphorescence, than the fauna of the well-known belt 

 of shallow Avater teeming with innumerable invertebrate forms 

 which fringes the land. And the forms of these hitherto unknown 

 living beings, and their mode of life, and their relations to other 

 organisms whether living or extinct, and the phenomena and laws 

 of tlieir geographical distribution, must be worked out." 



It was formerly supposed that animals could not exist at great 

 depths because of the excessive pressure to which they were subjected. 

 Mr. Moseley says: * " The pressure exerted by the water at great 

 depths is enormous, and almost beyond comprehension. It amounts 

 roughly to a ton weight on the square inch for every 1000 fathoms 

 of depth ; so tliat, at the depth of 2500 fathoms, there is a pressure 

 of two tons and a half per square inch of surface, which may be 

 contrasted with the fifteen pounds per square inch pressure to 

 which we are accustomed at the level of the sea." But it must be 

 recollected that water is nearly incompressible, and that marine 

 animals which are surrounded by such a fluid, and are to a certain 

 extent filled with it, would not necessarily be inconvenienced by 

 the superincumbent weight. 



Animals from great or even from what may be considered 

 moderate depths are nearly always brought up dead, the cause of 

 death being unknown. This is another problem worthy of being 

 worked out. 



The migration or distribution of marine animals throughout the 

 open sea is quite free, and is obstructed only by great or abrupt 

 changes of level in the bed of the ocean, which operate as barriers. 

 Even animals of a fixed or sedentary nature in their earliest state 

 of growth swim on the surface, and are therefore unchecked in 

 their onward course by any submarine barrier. 



The doubt whether any life exists in the intermediate space or 

 zone which lies between that of the surface and that of the bottom 

 of the deep sea has now, I believe, been set at rest. The natiiralists 

 in the ' Josephine ' Expedition believed that this intermediate zone 

 was lifeless ; and Sir Wyville Thomson seems to have been of the 

 same opinion. The towing-net adopted by Mr. Murray in the 

 ' Challenger ' Expedition for such researches was to some extent 

 successful ; but Captain Sigsbee, of the U.S. Coast-Survey steamer 

 * ' Xotes by a Xatui-alist on the " Challenger," ' p. 579. 



