UNI VALVE MOLL USCA. 4 1 I 



of Gasteropods very numerous, both in species and in special types, 

 all the species of which respire by the aid of branchiae or gills. 



The Tectibranchiata have the gills attached either to the right 

 side of the body or upon the back, arranged in the fomi of leaflets, 

 more or less divided, but not symmetrical, and nearly covered by the 

 mantle. 



Some species of the genus Aplysia were known to the ancients 

 under the name of sea-hares {Lepus mari/ms), from some fancied 

 resemblance to the terrestrial hare. They were objects of profound 

 horror, inspired either by their singular form, or from an acrid, caustic, 

 and inodorous liquid which they secrete. A magic influence was 

 attributed to them ; they were supposed, for instance, to have in- 

 fluence over the female heart. It is not easy, however, to explain 

 the evil renown acquired by an animal which is knowTi to be gentle 

 and even timid. They are naked and fat, somewhat resembling the 

 Limnaea in their oval, elongated form, their thickness in the dorsal 

 region, and their peculiar locomotion. Their head, which is very 

 indistinct, is furnished with four tentacles, the anterior tvvo of which 

 are the largest, and somewhat resemble the ears of a hare. The eyes 

 are found at the base of the posterior tentacles. These characters 

 are observed in Aplysia depilans (Fig. 179). Aplysia inca shows also 

 the same arrangement (Fig. 180). In this family the mollusc is 

 much more important from its volume than from its shell, which is 

 internal, rudimentary, and horny, and is placed just over the branchial 

 cavity. In Fig. 181 we have this small and thin cartilaginous shell 

 as it exists in A. inca figured. 



Species of the genus Aplvsia are found nearly in every region of the 

 globe, not only upon the shores of continents, but on every island 

 shore. They commonly inhabit sandy and muddy shores of small 

 depths, or even their rocky recesses, or under shelter of the stones 

 which have fallen from the cliffs. Their eggs form great long filaments, 

 which are discharged in immense numbers, and which fishermen call 

 sea-worms. 



They feed upon certain algae, with which the bottom of the sea is 

 covered ; but they eat also small marine animals, such as the naked 

 molluscs, annelids, and crustaceans. 



We are the less astonished to see the Aplysia so gluttonous when 

 we learn how liberally Nature has accorded to them organs of masti- 

 cation, trituration, and digestion. Their mouth is formed of thick 

 and muscular lips ; a very long oesophagus or gullet succeeds, and 

 this cesophagus does not communicate >vith a single stomach, but 

 with four — one enormous membranous crop, an exceedingly muscular 



