376 



SCIENCE. 



[N. S. Vol. XI. No. 271. 



by the unequal distribution of the glacial 

 drift, or by interference with preexisting 

 drainage lines. Inasmuch as Wisconsin is 

 not a mountainous state, it follows that 

 these depressions are nowhere of great 

 depth, and that we have no lakes which com- 

 pare in depth with those located in moun- 

 tainous regions. Most of our lakes are 

 extremely shallow, few being more than 

 forty or fifty feet in depth. Lake Geneva 

 142 feet, and Green Lake 237 feet, are our 

 deepest bodies of water, while our largest 

 lake, Lake Winnebago, probably does not 

 exceed twentj'-five feet. All lakes are tem- 

 porary features of the topography. The 

 outflowing water is all the time deepening 

 the outlet and increasing the amount of 

 drainage, while the inflowing water is 

 bringing in material which gradually fills 

 up the lake bed. This process goes on 

 with comparative rapidity, and even in 

 our new lake areas there are numerous 

 examples of dead lakes where swamp vege- 

 tation entirely covers what was formerly 

 an open sheet of water. The physical proc- 

 esses involved in the lives of lakes and the 

 relation of the lake vegetation to these 

 processes are very interesting, but this is 

 not the time or place to discuss them, and 

 thej' can only be referred to in passing. 



The subject of the fauna of fresh water 

 lakes has not been especially attractive to 

 zoologists. This is but natural when we con- 

 sider the great wealth of life in the ocean, 

 and the comparative poverty of fresh water. 

 Of the more important divisions of the 

 animal kingdom the echinoderms and tuni- 

 cates are entirely absent in fresh water, and 

 the coelenterates and molluscoidea are rep- 

 resented hj few forms. Even the Crustacea, 

 which form the greater part of the plank- 

 ton, and are present in such enormous num- 

 bers, have very few forms compared with 

 the Crustacea of the sea. It is to be ex- 

 pected that zoologists will be attracted by 

 this wealth of material in the sea, and that 



most of them will in the future as in the 

 past resort to the sea for their study. It 

 was in the ocean that the ancestors of our 

 fresh water animals dwelt, and it is amongst 

 those animals that the student may expect 

 to find the most information in regard to 

 the development of life on the earth. 



But the lakes have their fauna, a fauna 

 of great numbers if not of great variety, 

 and because of their isolation and some- 

 what peculiar conditions, present a very in- 

 teresting study in the distribution of ani- 

 mals. Of course the best known members 

 of this fauna are the fishes, whose num- 

 bers, habits, and food are fairly well known. 

 Fish are so important for human food that. 

 a study of their habits comes to be a mat- 

 ter of commercial importance, and our Fed- 

 eral and State governments expend large 

 sums of money for this investigation and 

 for the practical work of rearing and dis- 

 tributing the spawn or young fish. In 

 Wisconsin, too, as well as in some of the 

 other northern States, it is a matter of 

 great practical importance to maintain the 

 numbers of game fish in our lakes simply 

 for the purposes of sport. Until one has 

 made the rounds of the summer resort lakes 

 one has little idea of the multitudes of people 

 who come to our State in the summer sea- 

 son, attracted largely by the opportunities 

 for fishing. Hundreds of thousands of dol- 

 lars are brought to us every summer in this 

 way, and it is a good business policy which 

 leads us to do all in our power, and even 

 spend large sums of money, if necessary, to 

 maintain our stocks of game fish. 



It has long been known, of course, that 

 fish are dependent for their food upon 

 smaller animals, and it has also been known 

 that a knowledge of these same small ani- 

 mals was necessary to any accurate and com- 

 plete knowledge of fish, but this study was 

 so difficult and involved so much drudgery 

 that for a long time it was neglected. 



Anything like an exact knowledge of the 



