184 males of Cancharhinus porosus were caught by drift net off the state Of Mara-nhão, between Cururupu (1° 20' S / 45° W) and São Luís (2° 24' 30" S / 44° W) during the periods from October 1982 to January 1984, and from June to September 1984.
Development of the males was studied by observing the lenght-welght relationship and the growth of the claspers, testis, epididymis and liver. With the exception of the clampers and liver, the growth of these organs is continuous.
Three phases were observed in the growth of the clampers: the juvenile, adolescent and the adult phase. A discontinuity in the growth of the liver was observed during the transition from adolescent to adult phase, as was shown by the relationship between liver weight and body weight.
Smears of the contents of the seminal vesicle showed that the white liquid which occurs in this organ, does not contain sperms at fish lengths less than 70 cm.
On the basis of craspers grouth and sperm production, first sexual maturity and end of the adolescent phase was established at cm, and full maturity and adult phase ocurred at 75 cm.