•i->A 'l-lilrli/sl.rll, Ainnial Mrrllmj 



Jill im()|-,i;;lllizc(l llilid — the |)l;i>lll;l of llic I.I I nild llic Wiitcr of 



llic lake — and of mniici-()n> oi'^ani/.iMl and acti\rly li\in,u- |>aiis — 

 cells ill tlu' case of Mood, and the plant- and animals in llic lake. 

 As is tlu' cast' in llic animal, the !-cs|iiratn!'\ izascs arc alisurhcd 

 and transmitted to the livin,-- sti'Uctuivs hv means of the iinor- 

 ,iiaiiized lluid. It is my pnrpose te trace in entline the history 

 of these processes and their rc,-nlt upon the activity of the lake. 



The respiraTion of the lake, like that of the lii-hci' animal, 

 may he dixided into external and iiilci-iial respiration. \\\ the 

 former we iindei'sland the ahsoi'ption of certain ,i;ases iVom the 

 air and the return of other ,L;ases to it. a^ well a> the processes 

 \>\ whicli this exchan.uv is ctTcctcd. We iiudiide in it also the 

 methods hv whicli the pises are divtrihutrd in the lake and coii- 

 \\'\vi\ to and froin the surface of llie water, which takes them 

 from the atmos]ilier(> and ,i;i\-es them hack to it. \\\ inlernal 

 Tespiration we mean the gaseous exchaii,i;-es whicli take place in 

 the lake itself, hetweeii its \arious or,i:aiiisiiis and the water sur- 

 rouiulinii- them. With these exclianues come the chemical pro- 

 cesses by which the charactei- of the ,<:ases is altered or new- 

 gases nianitfacttn-ed. in the course of the \ital acti\ities of the 

 inhabitants of the lake. 



The extei'iial res])iration of the lake t-losely resemhles that of 

 the organism. The lake ahsorhs oxygen, carhoii dioxide, and 

 niti'ogeii from the atnios])here and returns to it nitrogen, carhon 

 dioxide, and sometimes other gases. The nitrogen ahsorhcd hy 

 the lakt', like that taken in hy an animal, has very little or noth- 

 ing, to do with the \ital ](roce^ses. In autumn, as the lake 

 cools, larger amounts of nitrogen are ahsorhcd. act'ording to the 

 general law of ahsorjition of gases. As llic lake warms during 

 the summer season, the capacity for holding gases in ahsorption 

 hecomes smaller and some of the nitrogen is lost. This process 

 is a purely physical one and has apparently no iiillucnce on the 

 life (d' aii\' of the organisms whose home is :ii the water. 



The relati(.ii of tfie oxygen to life is. howcvi'r, far dilfereiit. 

 and the processes of external respiration are of prime importance 

 to the li\ iiig heings of the lake. Spraking roughly, and in terms 

 of our coniparisou. we may say that an inland lake is an or- 

 ganism wdiich takes one full inspiration in the fall, and another. 

 less comi)lete. in the earlv siirini^-: that diiriim' the winter it 



