388 Wisconsin Academy of Sciences, Arts and Letters. 



BIOLOGICAL EEMAEKS. 



Latonopsis occidentalis was found in Lake Wingra, a small lake about 

 one and three-fourths miles long with a broad margin of marsh. It 

 lives chiefly in the marshy region although I have found it in deeper 

 W ater — one to three meters. It is most abundant in openings among 

 the reeds of the marsh, where there is a foot or so of water filled with 

 algae and vegetable debris. In one such spot it was especially abundant 

 during the summer of 1891. A single haul of the dredge would give 

 from six to thirty individuals. I have dredged it with Latona in the 

 open water, while I have never found Latona in the marsh. Sars' speci- 

 mens came from a clayey mud. I have never found this species in 

 muddy water. 



In the aquarium it behaves quite like Latona. It often remains sus- 

 pended and motionless in the water, and can often be turned over with 

 the dropping tube without disturbing it. When, however, it decides to 

 move it starts very suddenly. Its movements are less vigorous than 

 those of Latona, as would be inferred from the different structure of 

 the antennae. 



I have never seen more than eight young in the brood cavity. There 

 are two sexual eggs, for whose reception a special cavity is enclosed, 

 although there is no true ephippium. 



The males appear in the latter part of July and the first part of 

 August, and in September no specimens of either sex could be found, 

 while Latona was more plentiful at this time than earlier in the season. 

 Constant observation at any small lake will convince the student that 

 the appearance of the males does not depend on temperature or any 

 other simple cause. Each species has its own time for sexual reproduc- 

 tion, which is related to external influences in the same complex way 

 as is the flowering of plants. 



Species 8. Moina, spec. nov. 



A species of Moina, apparently new, has been found, but it is not as 

 yet thoroughly worked up and will probably form the subject of a spec- 

 ial paper. It seems related to M . brachiata, Jur. and was at first identi- 

 fied with this species. Further study, however, showed that there was 

 only one egg in the ephippium and that the structure in other particu- 

 lars differ from M. brachiata. The male especially shows peculiarities, 

 not found in other species. 



Species 21. Daphnia hyalina, Leydig. Plate XIII. Fig. 9. 



Into this species have been united D. galeata, Sars, D. pellucida, P. 

 E. Mtiller and D. gracilis, Hellich. Two well marked varieties are found 

 at Madison. One with pointed crest is found in Lake Wingra, and the 

 other whose crest is rounded is found in the larger lakes. Although the 



