Abstract
Determining the sex of T. gratilla was diffi cult and generally determined directly by the presence, length and shape as well assize gonopore genital papilla. We tried to determine of the gender17 individual of T. gratilla based on morphological approach.Injection of KCl and cleavage of the whole individual is alsocarried out to observe the color of the gonads as a reference fordetermining the sex. We found 6 samples of female and 11 malesamples based on gonad color. The results of morphological measurements showed that all parameters used have not been ableto determine the sex of T. gratilla, either singly or in combination parameters. The number of samples need to be added till at least30 individual each sex. This is consistent with logistic regression 3, where the P-value is less than the P-value logistic regression 1 and 2, which enables different results if the sample size is enlarged.