CRUSTACEANS 41 



Examination will reveal that its pincers are minute and 

 placed at the end of long whiplike limbs, a modification 

 believed to be brought about by constantly probing 

 the long and tortuous tubes of certain sandworms which 

 appear to be its principal food. 



Of late years several very large prawns from both 

 sub- Arctic and Mediterranean waters have become a regular 

 feature of our markets. Prawns, like all the long-tailed 

 crustaceans, are of very active habit and by suddenly 

 " snapping " the tail fin can project themselves through 

 the water backwards at high velocity and with considerable 

 precision. The prawns like all the members of the three 

 groups carry their eggs attached to the " swimmerets " 

 of their undersurface, the emergent young passing, as a 

 rule, through a series of transformations before attaining 

 maturity. Often these larvae bear grotesque horns and 

 other balancing appendages and it is of interest to note — 

 as indicating a common ancestry — that widely dissimilar 

 adult forms of different species often show a remarkable 

 uniformity in their larval stages. 



Several species of prawn bear light organs, whilst one 

 abysmal species covers retreat in a smoke-screen of highly 

 phosphorescent fluid, which it ejects from a special sac 

 much as the cuttlefish of shallow water discharges its ink 

 cloud. 



The lobsters include the largest members of the group. 

 Our Common Lobster {Homarus vulgaris) and its common 

 American relative (Homarus amerkanus) have a northern 

 range, the New World species being of stouter build, 

 its great crushing claw alone sometimes weighing 10 lbs. 



