148 



had taken five Cyclops, one Diaptomua and five examples of Anuraa 

 striata. Still another had eaten four of the Cyclops, four Diaptomus, 

 and one Anura?a. 



Twenty-five specimens were examined from those removed on the 

 24tli of the month, at which time ^he water of the tank was drawn 

 off, and all the remaining fishes bottled. Four of these had not 

 eaten, but the twenty-one others had devoured fifty specimens of 

 Diaptnmns sirUis, forty-seven of Ci/dops thomasi, fourteen of Anuneu 

 striata, and a single Daphnia hyalina, the latter being the largest 

 object eaten by any of the fishes. A few examples of their capacity 

 may well be given. The ninth example had eaten six Diaptomus, 

 two Ciiclops thomasi and one Anuraea ; the tenth had taken eight 

 Diaptomus, two Cyclops, and an Anurtea ; and the twentieth, seven 

 Diaptomus and three Cyclops thomasi. In two of these examples 

 were small clusters of orange globules, probably representing unicel- 

 lular Algse. 



Summarizing these data briefly, we find that of the 106 specimens 

 dissected, sixty-three had taken food, and that the ratio of those 

 which were eating increased rapidly, the longer the fishes were kept 

 in the aquarium. Only one fourth of those examined on the four- 

 teenth of the month had taken food, while more than five sixths of 

 those bottled ten days later had already eaten. The entire number- 

 of objects appropriated by these sixty-three fishes was as follows : 

 Cyclops thomasi, ninety-seven; Diaptomus sicilis, seventy-eight; 

 Anurcea striata, twenty-nine ; Daphnia hyalina, one. Seven of the 

 fishes had eaten unicellular xllgse, two had eaten diatoms, and one^ 

 filamentous Algae. 



From the above data we are compelled to conclude that the 

 earliest food of the white-fish consists almost wholly of the smallest 

 species of Entomostraca occurring in the lake, since the other ele- 

 ments in their alimentary canals were evidently either taken acci- 

 dentally, or else appeared in such trivial quantity as to contribute 

 nothing of importance to their support. In fact, two species of 

 Copepoda, Cyclops thomasi and Diaptom'S sicilis, are certainly very 

 much more important to the maintenance of the white fish in this 

 earliest stage of independent life than all the other organisms in 

 the lake combined. As the fishes increase in size, vigor and activity, 

 they doubtless enlarge their regimen by capturing larger species of 

 Entomostraca, especially Daphnia and Limnocalanus. 



A few words respecting the relative abundance of these species at 

 different seasons of the year, and their distribution in the lake, will 

 have some practical value. "We may observe here an excellent 

 illustration of the remarkable uniformity of the life of the lake as 

 contrasted with that of smaller bodies of water already referred to 

 in the introduction to this paper. While in ponds minute animal 

 life is largely destroyed or suspended during the winter, the opening 

 spring being attended by an enormous increase in numbers and rate of 

 multiplication, in Lake Michigan there is but little difference in the 

 products of the collecting apparatus at different seasons of the year.* 



*Fi>r (lolinito assurauoc of tliis fii«>t. 1 aiu iniU'bti>«l l.'ss to mv own ol>s«>i-vations iwhioh 

 aro, howcv.T. eonsist.-nt witli it as far asthov go.) than to tho statmnonts; of K. W. Thomas, 

 Es'i..ol Chii-ajro. who, while making a spoeialtv of theDiatomaooa>of tho lake, lias coUecteil 

 ami stiuiiod all its organic forms for several years, obtaininff them from the <'ity water 'v 

 attaehing a strainer to a hydrant many times during every month throughout the year. 



