Abstract: The paper deals mainly with the results of a laboratory study on material collected from Lake Dong-hu of Wuhan; both species re truly planktonic in nature.Temperature has close relation to their rates of development and growth. The duration of the entire embryonic development (D).was shortened with the increase of temperature (T). The regression equation may be expressed aslogD=2.5329-1.63671og T for Daphnia hyalina and logD=2.5627-1.6838 log T for D. carinata ssp.Growth rate varies with the number of instars. Most growth curves showed an initial high rate in the juvenile instars, an intermediate rate in the young adult instars, and a low rate in the older adult instars.There was a general tendency for females to attain a larger size when cultured at a relatively low temperature, as compared with those at a higher temperature.Usually 3—4 juvenile instars were present, to be followed by 12—18 adult instars under various temperatures. The total number of instars was reduced with lowered temperature.As a rule, the duration of the instar stages and the lifespan were inversely related to temperature.The maximum rate of egg production was 1.4936 at 20℃ for D. hyalina, and 1.4090 at 15℃ for D. carinata ssp. However, the intrinsic growth rate increased with the rise of temperature from 15℃ to 30℃.At various temperatures, the share in the duration of the entire developmental process was (5.08±0.42)% for embryonic stages, (10.76±1.53)% for juvenile instars, and (84.16±1.72)% for adult instars.From the data of the present study and those in literature, a curvilinear logarithmic equation:Ln D=3.5748±0.0769 Ln T-0.3122 (Ln T)2, is derived to summarize the relation between temperature and the duration of development in Daphnia.