INTRODUCTION. 9 



round to revenge the indignity, and, like Russian gens- 

 d'armes, seized upon the unsuspecting poles. These latter 

 were slightly shaken by the fishermen, as if in pain or ter- 

 ror ; the angry creatures clung all the closer, and were then 

 rapidly hoisted into the boat. The moral we drew at the 

 time, and have since maintained, was, that neither Crab nor 

 Christian should ever lose his temper." 



The following definition of Crustacea is that given by 

 Professor Milne-Edwards, in his classical work.* Animals 

 with the body divided into rings which are generally very 

 distinct, moveable, and horny or calcareous, without an 

 inner skeleton properly so called, and bearing a double 

 series of members, almost always very distinctly articulated, 

 and forming the antennas, jaws, etc., and legs, of which 

 there are usually five or seven pairs. The nervous system 

 is generally very distinct, ganglionic and longitudinal. The 

 respiration is in general aquatic, and is always by the 

 branchiae or the skin ; the circulation is in general very 

 distinct ; there is almost always an aortic heart, and proper 

 blood vessels. The sexes are separate. 



Many if not most of the Crustacea undergo, like Insects, 



* ' Histoire Naturelle des Crustaces,' vol. i. p. 231. Many of the cha- 

 racters in the following work are compiled from the Professor's three vols. 



