OBSERVATIONS ON THE ONTOGENY OF THECOSOMATOUS PTEROPODS (HOLOPLANKTICGASTROPODA) IN THE SOUTHERN RED-SEA AND FROM BERMUDA

The early ontogeny of Peraclis reticulata, Limacina inflata, L. trochi formis, Styliola subula, Clio convexa, Cl. cuspidata, Hyalocylis stria ta, Creseis acicula, Cr. virgula, Cuvierina columnella, Diacria quadri dentata, D. trispinosa, Cavolinia uncinata, C. longirostris, and C. in flexa is described. Their larval development is characterized, and str ategies of ontogeny of pteropods are viewed in the context of their bi ology and taxonomic position. The reconstruction of the juvenile shell into the voluminous adult shell in Dincrin spp. and Cnvolirzin spp. i s described in detail. The general features of the early ontogeny of T hecosomata does not deviate from those of other marine gastropods in e ssential ways as has been proposed by some authors, but postmetamorphi c retainment of the sinistral coiling of the shell as well as reshapin g of the juvenile shell in Diacria spp. and Cavolinia spp, are unique features of the euthecosomatous pteropods.