147 



new, but since described by me under the name of Cyclops thomasl* 

 This little entomostracan is only .04 inch long by .011 wide. The next 

 in size, and by fsir the most abundant member of this group was a 

 Diaptomus, likewise new, described in the paper just cited under 

 ihe name of Diaptomus sieilis. This appears in two forms, one 

 •evidently young in the stage just preceding the adult. Full-grown 

 individuals 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 Daphn'm lu/aliiia, an elegant and extremely transparent 

 species, occurring likewise m the lakes of Europe. A single insect 

 larval form (Chironomus) should likewise be mentioned in this con- 

 nection, since it had about the same size and consistence of the 

 Entomostraca, and was consequently equally available for food. 



The specimens of each of the above species from a certain quan- 

 tity of these collections were counted, in order to give a definite 

 idea of their relative abundance in the lake. The Diaptomus num- 

 bered 225, the Cyclops 75, Limnocalanus 7, Daphnia 3 and Chiro- 

 nomus larvffi 1. 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 Lmmocalanus ; a fact partly to be explained 

 by the predaceous 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 14th one hundred 

 specimens were removed, and twenty-seven of these were dissected. 

 Twenty were empty, but the remaining seven had already taken 

 food, all Cyclops or Diaptomus. Three had eaten Cyclops only and 

 six Diaptomus, while two had eaten both. Fourteen of these En- 

 tomostraca, seven of each genus, were taken by these seven fishes. 

 From those captured the next day twenty-five specimens were 

 examined, of which nineteen were without food. Of the remaining 

 six, three had eaten of Diaptomus and three Cyclops ; five of the 

 former being taken in all, and ten of the latter. Three specimens 

 were next examined from those caught on the 19th of March, two 

 of which had devoured Diaptomus, and a third a single Cyclops 

 tJiomasi and a shelled rotifer, Anuraa striata. The character of the 

 food at these earliest stages was so well settled by these observations 

 that I deemed it unnecessary to examine the subsequent lots m 

 detail, but passed at once to the specimens taken on the 23d. 

 Twenty-six of these were examined, and found to have eaten thirty- 

 three individuals of Cyclops thomasi, fourteen of Diaptomus sieilis, 

 and fourteen of the minute rotifer already mentioned {Anunea 

 striata). Two had taken a few diatoms {Bacilhma), and one had 

 eaten a filament of an Alga. Cyclops was found in sixteen of the 

 specimens, Diaptomus in nine and Anura^a in eight, only two of 

 them being empty. The amount of food now taken by individual 

 fishes was much greater than before, one specimen dissected having 

 eaten two Cyclops and six Diaptomus sieilis, male and female. Another 



* On some Entomostraca of Lake Michieran and Adjai-'ont Waters. Aineriean Naturalist, 

 Vol. XXL, No. VIII, August, 1882, pp. WO and 649. 



