144 CRUSTACEANS. 



IVoiri their retreats by the flowing tide, its tentacula, treacherously spread 

 abroad, are always ready to seize the unwary victims, with irresistible 

 I^ower, on simple contact. They crowd around their prey, while the wide 

 expanding orifice of the mouth gradually receives it yet alive. Many of 

 the victims seem completely paralysed ; nor ever by the slightest struggle 

 attempting to free themselves, even where they seem capable of doing 

 so. Besides sucii destruction in detail, others are engulphed by fishes 

 in the sea, whose capacious jaws are ever prepared to swallow the largest 

 and most formidable. 



Spite of their apparent strength and activity, the most vigorous of 

 the Crustacea are liable to perish from the slightest impurity of their 

 element. Hence, in confinement, all require unremitting care. 



It is important for the naturalist to discover the perils which 

 menace the subjects of observation and experiment. Whether inhabi- 

 tants of the sea, of fountains, lakes, or streams, constant humidity is 

 indispensable ; though not alike essential, for the terrestrial species. 

 Although some inhabiting the sea may quit their abode with impunity, 

 on recess of the tide, they must not be far distant on its return ; they 

 would inevitaljly perish. In confinement, the rapacious kinds ought to 

 have the water changed soon after feeding, and not long subsequently a 

 second time. Digestion is very rapid among these creatures, and some- 

 times fragments of animal matter remaining unconsumed escape notice, 

 which would speedily contaminate the element. Transferring the sub- 

 ject to a different vessel within six or eight hours is the safest expedient, 

 and replenishment of this within twelve or sixteen more. Frequent 

 examination is indispensable. 



But specimens often die suddenly without an obvious cause, whence, 

 if several be together, the naturalist must l^e careful of the survivors in 

 confinement. 



On this head it should be observed, that, for the most part, the for- 

 ceps of the claws of living subjects are open, as if always ready to seize, 

 and the tail, or posterior portion, is closed upon the neighbouring parts, 

 as if kept in its position by some exertion. This is more evident among 

 several of the Macrouri, the long-tailed or Lobster class. The reverse is 



