In Planorbis, which is sinistral (as are a few other genera or exceptional varieties of various Anisopleurous Gastropods).
Rabl has with remarkable skill applied the method of sections to the study of the minute embryos of Planorbis.
Planorbis has the spire of the shell in one plane.
One can imagine the interest and astonishment with which the great Greek would have been filled had some unduly precocious disciple shown to him the red-blood-system of the marine terrestrial Annelids; the red blood of Planorbis, of Apus cancriformis, and of the Mediterranean razor shell, Solen legumen.
One species of Limnophilus uses small but entire leaves; another, the shells of the pondsnail Planorbis; another, pieces of stick arranged transversely with reference to the long axis of the tube.