63 



greenish mucilaginous coating upon the interior of the muslin 

 net. In this were entangled a variety of rotifers, occasional 

 filamentous Algae, and many Entomostraca, the latter belong- 

 ing chiefly to the genera Cyclops, Diaptomus and Limnoca- 

 lanus among the Copepoda, and to Daphnia among the 

 Cladocera. 



As the Entomostraca proved to be far the most important 

 elements of this food supply, the particulars respecting them 

 may be properly more fully given. The smallest of all was a 

 Cyclops, then new, but since described by me under the name 

 of Cyclops thomasi/' This little Entromostracan is only .04 

 inch long by .011 wide. The next in size, and by far the most 

 abundant member of this group, was a Diaptomus, likewise 

 new, described in the paper just cited, under the name of 

 Diaptomus sicilis. This appears in two forms, one, evidently 

 young, in the stage just preceding the adult. Full-grown- indi- 

 viduals were .065 inch long by one-fourth that depth. The 

 Limnocalanus was a much larger form, evidently preying, to a 

 considerable extent, upon the two just mentioned. All the 

 Cladocera noticed were Daphnia hyalifia, an elegant and 

 extremely transparent species, occurring likewise in the lakes of 

 Europe. A single insect larval form (Chironomus) should like- 

 wise be mentioned in this connection, since it had about the 

 same size and consistence of the Entomostraca, and was con- 

 sequently available for food. The specimens of each of the 

 above species from a certain quantity of these collections were 

 counted, in order to give a definite idea of their relative abund- 

 ance in the lake ; the Diaptomus numbered 225, the Cyclops 

 75, Limnocalanus 7, Daphnia 3, and Chironomus larvae i. It 

 was a curious fact, however, that when the water was drawn off 

 at the end of the experiment, more than half the Entomostraca 

 were Limnocalanus ; a fact partly to be explained by the pre- 

 daceous habit of the latter, and partly by the facts relating to 

 the food of the fishes themselves, which are presently to be 

 detailed. The fry were placed in the tank and supplied with 

 their first food on the evening of the 12th of March. On the 



♦ " On some Entromostraca of Lake Michigan and Adjacent Waters." American Naturalist, 

 Vol. XVI., No. VIII. (August, i882\ pp. 640 and 649. 



