ON THE LAND MOLLUSCA. 
19 
and only for a short time, re-appearing with the shell much increased 
in size. This process is carried on at intervals during summer, and 
by autumn the shell is fully grown, the growth having only taken 
place underground. This method of growth is not however universal, 
for some species bury themselves in decaying wood, others bury only 
their heads in the ground, and others again merely hide themselves 
amongst decaying leaves. 
It is not easy to acquire and to retain in the memory a knowledge 
of any natural objects by reading about them alone, and therefore I 
would advise those who may wish to study our land Mollusca to 
commence by searching for them, then to find out their names, and, 
when these become familiar and are easily remembered, to examine 
more closely into the external form, internal anatomy, and habits of 
the various species. 
In commencing the study of our land Mollusca in this way the 
first thing necessary is to know where and when to look for them. 
An answer is easily given: “Everywhere and at all times.’ 5 There 
is scarcely any situation where, at some time or other, they may 
not be found in more or less abundance. But to know where and 
when they may be searched for with the greatest chance of success 
is quite another matter, and necessitates some knowledge of their 
habits. All more or less affect damp and shady places, hiding 
themselves from observation in dry or sunny weather, except in 
the early spring for a short time after they leave their hibernating 
quarters. The first advice I would give is therefore to “leave no 
stone unturned.” Erom my own experience of a few months’ 
collecting, at occasional intervals, I believe that there is scarcely 
a species present in any locality which may not be found under a 
stone at some time or other. The under side of decaying pieces of 
wood lying upon the ground, of fallen branches of trees, especially 
if moss-covered, of fallen leaves, and of the leaves of growing 
plants, should also be examined; and indeed, except late in the 
evening, in the night, early in the morning, or soon after rain, the 
land mollusks will only, as a general rule, be found on “ under¬ 
sides.” They cannot bear the heat or the drying power of the sun, 
nor do they like the glare of full daylight; they love darkness and 
moisture. This is especially the case with the slugs, and with the 
snails which have thin or transparent shells. Keep a slug for a 
short time without access to moisture and it will dry up and die ; 
put a snail with a thin transparent shell in the rays of the sun and 
it will retreat as far as possible into its shell, and, from loss of 
moisture, will soon die. Both slugs and snails are constantly, 
except perhaps when snails are hibernating and in a dormant state, 
absorbing moisture and excreting it from their bodies as mucus or 
slime, and wherever they go they leave in their track some of this 
mucus. Access to moisture is therefore most necessary to the 
existence of slugs at all times and of snails when in a state of 
activity. They can exist for some time under water, but in very 
heavy or prolonged rainfall they will come out of their holes in the 
ground for fear, it is presumed, of being drowned, and this is the 
