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Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume VIII (1888-1891)

Birge, Edward A.
List of crustacea Cladocera from Madison, Wisconsin ,   pp. 379-Plate XIII ff. PDF (7.9 MB)

Page 388

388      Wisconsin Academy of Sciences, Arts and Letters.
                       BIOLOGICAL REMARKS. 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
 water -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 d6bris. 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. Mfller 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

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