A total of 149 samples coming from Cananéia (25º lat. S) was analysed. The samples are part of Series E, Plankton Section, Oceanographic Institute of São Paulo. They were taken fortnightly from January 1958 to May 1959 at three fixed stations. Altogether 591 males, 573 females and 1426 juveniles of Lucifer faxoni Borradaile 1915 were studied. The results are as follows: 1 - There is a linear correlation between length of neck and total length. 2 - Sexual maturity is reached at 1.18 mm neck length for the males and 1.19 mm for the females. 3 - Sexual maturity peaks occur in summer and autumn. 4 - Sexual maturity stages were established according to fetasma and ovary development respectively for males and females. 5 - Based on neck length, from size groups may be traced in males. First group of smallest specimens, neck length 0.64-0.80 mm, was present in March, November 1958 and January-February 1959. The second group, neck length 0.83-1.16 mm was present all year round, except in July 1958. The third group also occurred all year round, the neck is longer than 1.18 mm. The largest males neck length 1.70-1.92 mm were present in July, September, October, November 1958 and May 1959. 6 - Females may also be classed in four categories. The first group neck length 0.54-0.90 mm was present in February, March, April, May 1958 and January, May 1959. The second group has neck length 0.95-1.16 mm. The third group has a neck length 1.19-1.79 mm. The fourth group, neck length 1.80-2.27 mm was present in June, October, November 1958 and January, May 1959; they reach larger sizes than the males. 6 - Juveniles were found throughout the year, neck length varying between 0.32-0.94 mm. 7 - The density of sexed and juveniles is slightly different. The frequency of juveniles shows two peaks, a taller one occurs from December to April and a smaller one from September to October. The frequency of sexed specimens shows only one peak that occurred from December to April. These peaks are slightly displaced as compared to the total zooplankton volume in the same area (VANNUCCI, 1962). 8 - The scarcity of specimens in January 1958 may have been caused by a fall in temperature.
