272 
Mr. L. Reeve on the Habits and 
through it ; as the moisture evaporates^ the epidermis resumes its 
light appearance. Sir David Brewster, in reply to a letter from 
Mr. Broderip on this subject, says : It appears to me, from 
very careful observations, that the epidermis consists of two 
layers, and that it is only the upper layer which is porous, 
wherever the pattern is white. These white or porous portions 
of the epidermis dilfer from the other parts of the upper layer 
only in having been deprived of, or in never having possessed, 
the element which gives transparency to the membrane ; in the 
same manner as hydrophanous opal has become white, from the 
expulsion of its water of crystallization.^^ 
There is little variety in the animal of Bulimus : the Chilian 
species are mostly of a light colour, and a few in this and the 
Columbian district are spotted, some having a transparent shell 
through which the spots are visible. The Philippine species are, 
without exception, of a sombre olivaceous brown, and dwell in 
family groups, as it were, among the shady foliage of the branches. 
Out of a group of some dozen living specimens, not more than 
three or four may be found in an adult state with the lip of the 
shell reflected. They may be dislodged by shaking the branches, 
but are chiefly disturbed by the heavy rains with which these 
islands are at times visited. Mr. Cuming preferred, however, to 
collect them in dry sunny weather, because he was sure of finding 
the objects of his search in their shady places of retreat. In the 
immense sandy tract on the west side of the Andes, the reverse 
of this condition of nature prevails. The Bulimi are here phy- 
sically very distinct ; some reside all the year round upon the 
numerous Cactiy but during the dry season, which lasts for several 
months, they live mostly in a state of torpor, inclosed within 
their shell by an epiphragra, and buried in the sand or under 
stones. On the approach of the dews they revive to a state of 
animation, and crawl about at night in quest of food. 
In illustration of the remarkable drought that prevails in 
Northern Chili, and of its effect upon molluscous life, I am 
tempted to repeat, in brief, an anecdote related to me by Mr. Cu- 
ming. On the arrival of our friend at the port of Copiapo in 1829, 
he discovered the beautiful Bulimus Broderipii in considerable 
numbers, in the fissures of the rocks that may be seen here and 
there in the sandy plains of that country. Finding a large pro- 
j)ortion of them dead, with the soft parts entirely decomposed, 
he requested a solitary inhabitant of the place to collect as many 
specimens as he could pick out alive, whilst he occupied himself 
in botanizing. Returning from his excursion, Mr. Cuming was 
greatly disappointed to find that among the quantity his Chilian 
collector had accumulated, there was scarcely one in a living state. 
Vpon remonstrating with him for his inattention, the native re- 
