Observations on Development of the Heteropod Molluscs Pterotrachea Hippocampus and Firoloida Desmaresti

The nidamentary filaments and various developmental stages up to veliger larva of Pterotrachea hippocampus Philippi 1836 and Firoloida desmaresti Lesueur 1817 are described and illustrated. General information on the late veliger and the newly metamorphosed female of the latter species is included. Apparently the filament of P. hippocampus is a typical “egg string” which serves to encase only one batch of spawn whereas that of F. desmaresti is a permanent structure. In the laboratory, both species, developed from fertilized egg to free-swimming larva in approximately 48 hours.