42 
question is afforded by considering wbat is the relation between 
the animal and its shell. The union between them is so close 
that although there are plenty of shell-less snails, commonly 
called slugs, those which possess shells perish soon after extrac¬ 
tion, and that although there is no organic union between them. 
Has the animal, one would ask, any liberty of choice in 
selecting the colour of its shell ? A specimen I obtained at 
E-edcar throws some light on the subject. It is a banded snail, 
and has been severely crushed. The snail has repaired the 
shell. It has retained the shape and the pink colour of the 
remainder of the shell, but has not been able to re-produce 
the brown bands. Thus, we may conclude, I think, that each 
snail can once, without conscious effort, produce a shell of one 
uniform plan ; but that when, from any cause, conscious effort 
is called forth on the part of the animal, no elaborate previously- 
begun pattern can be carried out, and convenience and safety is 
the only thought present to the mind of the utilitarian and 
unaesthetic mollusc. Another specimen, obtained near Brid¬ 
lington, shows that this snail can alter the spiral curve of its 
growth, if desirable—a phenomenon much more common, and 
naturally so, among the freshwater discoidal shells included 
under the genus Planorhis. The shells before us are divided 
into two principal groups. The first group is distinguished by 
the lip being coloured brown, and is called Helix neinoralis. The 
second has the lip white, and is known as Helix hortemis. A 
form with a pink lip also occurs, and has been (with doubtful 
propriety) called hybricla. Few points have been more eagerly 
discussed by conchologists than the right of these differently- 
coloured shells to rank as distinct kinds. My own view is that 
nemoralis and liortensis, at any rate, form two pecies; hyhrida 
may be a form of the latter. The reasons for this view are as 
follows:—A practised eye may detect a difference in the size 
and shape, as well as in the colour of the two shells. A typical 
specimen of H. hortensis is smaller and more conical than a 
t3q)ical specimen of H, nemoralis. There is also a difference in 
the texture of the shell. Hortensis is the thinner and more 
transparent. In the second place, the two so-called varieties 
have never to my knowledge been observed to breed together, 
