382 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1923 



nautilus without a shell, which was swimming about in a bowl of 

 water containing material from a haul off south Japan, when my 

 finger was violently seized by something. Exploration with a glass 

 rod and a pair of forceps revealed the presence of a large and ugly 

 amphipod an inch or so in length, entirely transparent, though as 

 tough as any other. 



From the surface of the ocean down to great depths animals exist, 

 but the number of major groups and of species rapidly decreases 

 and their size becomes more nearly uniform below the limit of light, 

 until in the deeper layers only grotesque fishes, cuttle fishes, jelly- 

 fishes, crustaceans, nemerteans, and echinoderms, all feeding on each 

 other, are found. 



THE SEA SHORES 



The shores of the sea are bathed by the water from the open 

 ocean, charged with microscopic plants and small crustaceans, and 

 with such of the creatures feeding on these as are able to support 

 the light of day. But because of the fact that the rocks and stones 

 and mud, and to a lesser degree the sand, offer facilities for attach- 

 ment, conditions here are entirely different from what they are in 

 the open sea. 



Along the shores an attached plant, as a result of the movement of 

 the water about it, has constantly delivered to it a fresh supply of 

 the dissolved substances necessary for its growth, and it is main- 

 tained permanently under conditions most suitable for its existence. 

 Hence the enormous development of the brown, green, and red algse, 

 or "seaweeds." Some of the flowering plants, too, have become 

 adapted to marine conditions, and one of these, the eelgrass, belong- 

 ing to the pondweed family, forms extensive beds in suitable lo- 

 calities. 



These plants are important in providing shade and hiding places 

 for the animals found among them, and when alive they are eaten 

 by a few mollusks, like the periwinkle, by a few crustaceans and 

 fish, mostly under stress of hunger, by some sea urchins and, where 

 these occur, by sea cows, manatees, and dugongs, by some turtles, 

 and by a single lizard. When they die their leaves or fronds break 

 up and the fragments form the vegetable detritus so very important 

 as the basic food of the marine animals along the shores. 



In the open sea the animals can avoid the dangers attending too 

 violent wave action by simply descending to the quiet depths. Along 

 the shores there is no escape from the constant movement of the 

 water. This incessant turmoil on the shore line, however, is easily 

 translated from a menace into a distinct advantage ; animals simply 

 attach themselves firmly to seaweeds, stones, or other objects, and 

 let the water do the work of bringing food to them. 



