1) Total copepod numbers per litre in Lake George, Uganda, vary slightly during the course of a year. Numbers increase during the dry seasons June-August and January-February, and decrease during the rains. This variation is more marked in the mid-lake area, where copepod numbers are higher, but the change in numbers is not more than two-fold. By comparison with populations in temperate regions the population in Lake George is stable in size and shows little seasonal variation.(2) The carnivorous cyclopoid Mesocyclops leuckarti forms only 4-21 %, by numbers, of the total copepod population and does not occur in numbers large enough to be analysed profitably.(3) The bulk of the population is the much smaller Thermoeyclops hyalinus and analysis of this population into the main development stages of its life history shows an almost constant age structure over the lake as a whole, throughout the year.(4) The development time of the eggs, as determined previously (Burgis, 1970), is 1-5 days. This, plus mean development-times of 6 and 11 days for nauplii and copepodites respectively, has been used to determine the daily rate of recruitment from each stage of the life history to the next. The recruitment from nauplii to copepodites and from copepodites to adults are very similar and almost constant. Recruitment from eggs to nauplii is. however, mueh greater, and it thus appears that the major loss to the population is at this eariy stage in the life history. This may well be due to predation by the larvae of Chaohorus.(5) Using this recruitment rate from eggs to nauplii, the potential turnover time of population numbers was calculated to have a mean value of 4-2 days for the lake as a whole. This is similar to maximum summer turnover times found by authors such as Hall (1964) for Daphnia populations in temperate waters.(6) The biomass of individuals at various stages in their life history was determined as carbon, and application of these determinations to the numerical counts was used to calculate the standing-crop biomass in the lake. With a constant population of stable age-structure it is possible to estimate the daily biomass production from the turnover time of numbers. For the population of Thermocyelops hyalinus in Lake George this gives a mean figure of 21! /.igC/1/day during 1969-70.(7) Instantaneous birth rates and instantaneous rates of change in population numbers {b and r) have also been calculated for the population of Thermocyclops. The values of r show some variation at one centre site, fluctuating around zero, but when calculated for lake mean figures r is hardly different from zero throughout the year. The values of b also show fluctuations when calculated for one site but when calculated for lake mean figures show no more than two-fold variations, being higher at the beginning of the two rainy seasons. The values of b are not as high as those attained during the summer in some temperate Daplmia populations such as those described by Wright (1965). The values of ZJ tend to be higher inshore than in mi...

The rate of egg development in ThermocycZops sp., determined in the laboratory, increases linearly from 15-3OC. Above 32.5C development is retarded and, although eggs hatch at 356, the females die after some time at that temperature.At 4OC, mortality is 100% within 2 hr. The mean temperature of Lake George is computed to be 26.3C and, by extrapolation from the laboratory results, a mean development time of 36 hr is obtained. Both these means vary little throughout the year. From the work of others, it appears that the effect of temperature on egg development is similar in Mesocyclop~ Zeuckarti but less marked in several Calanoid copepods.

The relationship of total body length to formalin dry weight for individuals of Thermocyclops hyalinus and Mesocyclops leuckarti, from the tropical Lake George, Uganda, is given and shows that previous estimates of individual biomass and, therefore, of zooplankton standing crop and production based on them, were too high. The annual mean standing crop of total Crustacea, in 1969-70 was 828 mg (dw) m~^ and for T. hyalinus, the dominant species, 559 mg (dw) m^^ Biomass tended to be higher in the mid-lake area than inshore. The annual mean production of T. hyalinus is now estimated to be 44 mg (dw) m-2 day.

All rights reserved INFO RM ATIO N TO ALL USERSThe quality of this reproduction is dependent upon the quality of the copy submitted.In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Relationship between egg number and body length. ^i.Relationship of egg volume to body length. 36.Egg number, body length, temperature, and chlorophyll. 41»The shape of Ceriodaphnia eggs in relation to their volume. * Egg size and temperature. 50«The seasonal occurence of sterile eggs in I9 6 3 . 50.The Maltese species. 3 ,'Discussion. 5 4 .Acknowledgements. gp. Summary. 5X.Bibliography. 5Âppendices. ^2 An important fact brought out by these graphs is the difference in size of these species. Ceriodaphnia reticulata is consistently larger, on average, than C. pulchella and C. megalops is larger than either of these two species.C. laticaudata overlaps between C. reticulata and C. pulchella.There is some overlap in the sizes of all four species when one considers the full range measured, as in Table 2. (Table 3») that the larger eggs approximate most nearly to a sphere.There is a negative correlation coefficient of -0.^7, which, with 8l degrees of freedom has p