[The first stades of genesis of the pelvic fin anlage in the Trout (Salmo fario andSalmo gairdneri) : II. Comparative histochemical data].

In a study with the light microscope, we investigated the tissular localization of glycogen, R.N.A., and 4 phosphohydrolases in the pelvic fin bud of two species of Trout,Salmo fario andSalmo gairdneri, Pisces, Teleostei. In both, the epiderm bud, including the "pseudo-apical cap", is devoid of glycogen and the amount of R.N.A. histochemically demonstrable is not greater than in epidermal regions outside the bud. InSalmo gairdneri but not inSalmo fario, we observed four phosphatases, only in the inner layer of the epiderm of the fin bud: alkaline phosphomonoesterases, naphthol AS-BI acid phosphatase, nonspecific ATPase and AMPase. The "initial mesenchyme", from the somatopleura's proliferation, contains a great quantity of R.N.A. In both species we found there the four enzymes. The "secondary mesenchyme", obtained from the dispersion of four ventral somitic processes, has a metabolism that is similar inSalmo fario andSalmo gairdneri; alkaline phosphomonoesterase is found only inSalmo gairdneri.