ON GASTEROPODA. 335 
season of reproduction, that the helices issue from their 
retreats. ‘They are advertised of the presence of external 
bodies only by means of the fineness of their touch. In fact, 
at the slightest contact with any part of their body, but 
especially of their tentacula, they withdraw themselves more 
or less completely within their shell, and do not come forth 
again but by degrees, and with the greatest possible precau- 
tion. ‘The choice which the snails make of certain herbs, does 
not permit us to doubt of their being provided with the sense 
of taste. It would appear that they do not perceive bodies 
at a distance, but by the assistance of the sense of smell, the 
seat of which is probably in the first pair of tentacula, and 
that in a manner complete enough, since it is known that 
these animals are attracted a good way by the odour of the 
plants which they prefer. It is not probable that the organ 
of vision found at the extremity of the large tentacula is of 
any great use to them. In the first place, it is by night that 
they are most active; then it is evident that the structure of 
the organ is very incomplete, and experiment proves, besides, 
that on approaching a body to these tentacula, the snail does 
not perceive it any sooner than when it is approached in the 
same manner to the first pair. Moreover, their extreme 
timidity, the precautions which they take in walking, to ex- 
tend as much as possible the two pairs of tentacula in front of 
their body, to explore all obstacles, evidently indicate an 
animal pretty nearly blind. 
The snails are nourished essentially with vegetable sub- 
stances, with tender succulent herbs, and fruits of the same 
nature. But it seems that they also eat animal substances, 
such as cheese. They gnaw the leaves and fruits by means of 
their jaw, which is opposed to the tongue, and that with very 
considerable strength, and sometimes quickly enough to cause 
great devastation in our gardens. But it is especially in fine 
weather, and when they come forth from their hybernating 
