G. NATURAL HISTORY AND ZOOLOGY. 32 1 



plastic to serve for modeling purposes. A section of this re- 

 veals, first, an upper layer three to four centimeters thick, 

 bright and yellowish, and formed of mineral mud, with the 

 remains of dead and of living animals. Next comes a bluish 

 layer, about one centimeter in thickness; then a bluish, argil- 

 laceous, rather plastic and dense stratum, w T hich is continued 

 indefinitely downward. 



The fauna of the bottom appeared to reside entirely in the 

 upper layer, and was investigated by two different methods. 

 The first consisted in allowing: the mud to remain in a flat 

 dish, full of water, so that the living animals might come out 

 and swim about and be examined. Then, after a few days, 

 the mud was dried, when various shells came to the surface 

 and made their tracks ; and, finally, by scraping the surface, 

 different worms were secured. In this wav it was ascertain- 

 ed that the mud is very rich in living animals, the number 

 being estimated at about one hundred to the square meter 

 of mud. 



Another method consisted in washing out the mud, leaving 

 the animal matter behind, which gave the dead animal mat- 

 ter, especially the shells, mollusks, crustaceans, etc. 



Dr. Forell estimates the number of shells, entomostracans, 

 etc., at from five to ten thousand per quart of the mud. This 

 abundance of organic remains may possibly explain the rich- 

 ness in nitrogenous and phosphatic matters of a certain class 

 of marls employed for agricultural purposes. As far as the 

 vegetable life was concerned, no growing plants were found 

 beyond a depth of about eighty feet, although some violet 

 al^re and numerous diatoms were met with. 



Among the conclusions reached by Dr. Forell in his in- 

 quiries are these: that in the Swiss lakes there are two dis- 

 tinct faunas on the bottom a littoral fauna, or that of the 

 banks, extending to a depth of forty-five to sixty-five feet, 

 and the deep-water fauna, reaching to 900 feet and more; 

 there is furthermore a pelagic fauna, consisting, of course, of 

 fishes, crustaceans, etc., that change their position in the wa- 

 ter. All the forms of the deep-water fauna are analogous to 

 that of the shore, but not exclusively of the same species. 

 Differences were met with of considerable importance ; thus 

 in some places there were beds of the egg-shells and cara- 

 paces of crustaceans. 13 J5, November 15, 1873, 382. 



O 2 



