12 A HISTORY OF RECENT CRUSTACEA 
CHAPTER II 
SPECIMENS 
Collecting 
To study adequately any branch of natural history, it is 
essential to have specimens. Many exemplary forms of 
Crustacea are not difficult to obtain. Representatives of 
the two highest orders in the group, the crab, the lobster, 
the prawn, the shrimp, are exceedingly familiar, as these 
creatures lie on the fishmonger’s board, or are brought to 
table for food. When the eatable parts have been con- 
sumed or otherwise removed, the débris is still of value 
for mental nourishment. This refuse may be made to 
yield more profit and pleasure than many a costly collec- 
tion which can only be viewed intact. By carefully 
separating the constituent parts of the head, the trunk, 
and the tail, in each of the crustaceans above mentioned, 
and comparing them piece by piece, the beginner will be 
able to give himself a cheap but invaluable lesson. He 
will be surprised at first to detect likenesses in the corre- 
sponding parts of animals externally very distinct, and 
afterwards he will be surprised at the differences in the 
corresponding parts of animals which he has learned to 
regard as closely connected. As his range of study widens, 
he will find relationships established between forms which, 
to any one unacquainted with the intermediate links, must 
seem to have absolutely nothing incommon. For instance, 
while examining the gills of a lobster, he may chance to 
observe some small orange-coloured specks, and may 
rightly conjecture that these are parasitic animals. But 
it is scarcely conceivable that any amount of genius would 
