70 



THE MUSEUM. 



ature on the subject is almost wholly 

 confined to the publications of the 

 last twenty years, and consists in large 

 part of the reports by various special- 

 ists on such voyages as those of the 

 British vessels, Lightening. Porcu- 

 pine, Valorous and Challenger ; the 

 French Talisman and Travilleur ; 

 the Norwegian, North Atlantic Expe- 

 dition; and the expeditions of our own 

 Coast Survey, Fish Commission, and 

 Navy, on the Blake, the Fish Hawk, 

 the Albatross and other well known 

 vessels. The most distinguished nat- 

 uralists of this country and of Europe 

 have added to their reputation by the 

 investigation of wonderful fauna re- 

 vealed by these explorations. The 

 most extensive and important single 

 series of Scientific Reports ever pub- 

 lished as the result of a single expe- 

 dition are those which bear the name 

 of the Challenger upon their capacious 

 covers. Next to these come the Re- 

 ports of the United States Fish Com- 

 mission, under the leadership of Prof. 

 Baird, and then follows a host of min- 

 or documents which it is impossible to 

 enumerate at the present time. 



What I have to present to you is 

 rather a discussion of conditions and 

 principles than an exhibit of particular 

 facts or observations. 



In order that their existence may be 

 maintained the abyssal mollusks re- 

 quire oxygen to aerate their circulation, 

 food to eat, and a foothold upon 

 which they may establish themselves. 

 It is necessary that ihe conditions 

 should be such as will not prevent the 

 development of the eggs by which suc- 

 cessive generations are propogated, 

 and that they do permit it may be 

 assumed from the very fact that mol- 

 lusks in large numbers have been 

 shown beyond all question to exist on 

 the oceanic floor wherever this has 

 been explored. 



Formerly when dredging with the 

 usual appliances in small boats, one 

 hundred fathoms (six hundred teet) 

 was considered extremely deep. If 

 one stands at the foot of the great 



Washington obelisk and looks up, the 

 idea of collecting a> satisfactory repre- 

 sentation of the insects and plants on 

 the ground at its base by dragging a 

 six foot trawl or dredge by a line let 

 down from the apex of the monument, 

 strikes one as preposterous. Yet the 

 monument is less than one hundred 

 fathoms high. Multiply this height 

 ten or fifteen times, and the idea 

 seems, if possible, still more unreason- 

 able, yet it is a fact that successful 

 dredging has been done from a height 

 above the sea-bottom, of not less than 

 twenty-five times the height of the 

 Washington monument. Living ani- 

 mals have been secured from a depth 

 of about two and a half miles. 



It is therefore evident that in speak- 

 ing of dredging, we must revise 

 our terms and define them so as to 

 conform more nearly to the new con- 

 ditions under which such work is done. 



The waters immediately adjacent to 

 the shore were long ago divided by 

 Forbes and other pioneers in marine 

 exploration into zones or areas accord- 

 ing to the conditions characterizing 

 them; for instance, the Lammarian 

 zone or region of brown kelp, the 

 Coralline zone or region of stony algae, 

 etc. But for general purposes and to 

 contrast the areas of the whole :-ea, 

 one with another according to their 

 chief characteristics, we may now di- 

 vide the entire sea bottom into three 

 regions. 



The first is that to which the light 

 can penetrate and therefore where 

 marine vegetation can exist. This is 

 the Litorial region, and in a general 

 way, modified by especial conditions 

 at particular places, it may be regard- 

 ed as extending from its actual shore 

 out to the limit of one hundred fath- 

 oms. Beyond this it is practically 

 certain that no light reaches the bot- 

 tom of the sea and no sea weeds grow. 

 Outside of this the borders of the con- 

 tinents slope gradually to the bottom 

 of the ocean, which is found usually 

 at a depth of about 2,500 fathoms. 



On the upper parts of these conti- 



