12 A HISTORY OF EECENT 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 debris is still of value 

 for mental nourishment. This refuse may be made to 

 yi^ld 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 in common. 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 



