OCCASIONAL NOTES. 225 
in danger of extermination, and the balance of nature was evenly kept up. 
As soon, however, as—owing to the opening of the iron mines, the extension 
of the railway system, and the rising up of large towns, such as Barrow, in 
the neighbourhood—the population began to grow abnormally, and, at the 
same time, the demand for every sort of food in the manufacturing districts 
to increase enormously, the balance was upset, and the day, though still 
distant, can be seen approaching, when the humble cockle will be as rare 
as the oyster, and, if preserved at all, will have to be cultivated in the 
Same way as that animal is at present. Whatever may be said of the sea- 
birds, I believe it is simply the old story of the demand exceeding the 
supply which must account for the diminution in the number of British 
shell-fish— W. Arraur Durnrorp (Barrow-in-Furness). 
Exoviation or Logsters.—In ‘The Field’ of May 25th, Mr. W. A. 
Lloyd, of the Crystal Palace Aquarium, has an interesting article with this 
heading, in which he points out that the notion which prevailed formerly 
(that is before the establishment of public Aquaria afforded such facilities 
for the study of Crustacea) as to the mode in which lobsters annually cast 
their shells, is erroneous, and he very clearly describes the curious process 
from his own observation. The article, which occupies two columns in 
‘The Field,’ is too long to be quoted in extenso, but we feel sure that the 
following extract, which contains the pith of Mr. Lloyd’s remarks, will be 
read with interest by all who have not already perused it in the columns of 
our contemporary :—‘ What takes place,” says Mr. Lloyd, “is this: the 
lobster, feeling the time of exuviation approach—which in aquaria may 
be any time of the year—seeks a retreat where it may be safe during the 
period of soft helplessness, which lasts for three or four days after 
exuviation ; usually selects it below some overhanging rock, and if there 
is protection on each side so much the better. If there is a good deep 
bed of sand and shingle, as there should be, six or eight inches thick, the 
lobster proceeds to excavate this away behind, and with its anterior limbs 
pushes it up in front, and makes a kind of defensive earthwork. In this 
it is aided by an occasional fanning motion of its false feet in driving away 
a current of sand outwards, below its tail, the head being then turned 
inwards, towards the hinder part of the snug little cave thus formed, into 
which the lobster never allows any other creature to enter, not even 
a gentle little shade-loving fish, like Motella. When the moment arrives 
for casting the shell, the lobster falls over on its side, a rupture is made in 
the membrane uniting the posterior of the cephalo-thorax with the anterior 
ring of the abdomen, and presently a part of the lobster’s new coat may be 
seen between these two. The rent is made by the lobster suddenly and 
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