. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 322 J. D. COSTLOW, JR. AND C. G. BOOKHOUT 5). Molting of the fifth naupliar stage occurs from day 5 to 9, with a majority on day 7. This stage showed greater mortality than any other stage, it being approxi- mately 33 per cent. The sixth and final naupliar stage molts into a cyprid on the seventh to twelfth day, with a mortality of 22 per cent. There is apparently considerable variation in the duration of the cyprid stage. Pyefinch (194Sb) reports that the cyprid of Balanus balanoidcs remains free- swimming in laboratory tan
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 322 J. D. COSTLOW, JR. AND C. G. BOOKHOUT 5). Molting of the fifth naupliar stage occurs from day 5 to 9, with a majority on day 7. This stage showed greater mortality than any other stage, it being approxi- mately 33 per cent. The sixth and final naupliar stage molts into a cyprid on the seventh to twelfth day, with a mortality of 22 per cent. There is apparently considerable variation in the duration of the cyprid stage. Pyefinch (194Sb) reports that the cyprid of Balanus balanoidcs remains free- swimming in laboratory tanks for five days at 4-5° C. but estimated a shorter period in nature. Under laboratory conditions we found that those which settled and underwent metamorphosis to the pinhead did so within one to three days, whereas 30 I- OL §20 O I 5 5io u Ld °- 5. H 12 STAGE I2L FIGURE 5. Mortality in relation to naupliar stages (I-VI) and cyprid stage (c) of 121 Balanus cburneus reared under segregated conditions. those which persisted as cyprids for longer periods, up to 14 days, failed to settle and died. Mortality in the cyprid stage was approximately 16 per cent. In some cases the mortality was due to incomplete closing of the carapace following the sixth naupliar molt. These abnormal cyprids could live as swimming larvae for two to three days but they failed to settle. The over-all time of development for B. cburneus is quite short when compared with the times given for most other species. Bassindale (1936), although not giv- ing water temperatures, reported 13 days as the minimum time for completion of the sixth stage of Chthamalus stcllahts and a 22-day minimum for the sixth stage of Verruca stroemia. Unfortunately, comparison between species is not too reliable, for the effect of temperature on individual species has not been determined and can only be inferred from studies on other species at different temperatures. Hudinaga and Kasahara (1941) found that the minimum time for dev
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