INTRODUCTION. xxvii 



animal, upon being wounded in either of the limbs, would 

 of necessity bleed to death. That such would be the case 

 would appear to be extremely probable, but, like all nega- 

 tive evidence, is only of value in the absence of direct 

 testimony. In the Sessile-eyed orders the animal appears 

 to want the power of voluntarily throwing off any of its 

 appendages, no matter how severely it may be wounded. 

 If a leg be cut off, or in any way injured, the wound 

 very soon after becomes cicatrized with a black scar, 

 which remains until the next exuviation of the animal, 

 when the entire limb is thrown off with it, and a new one 

 commences growing. 



TASTE AND DIGESTION. 



The sense of the enjoyment of food, even in the highest 

 types of the animal kingdom, exists rather in the power 

 of parts to receive impressions than in the presence of 

 any especial organ for the purpose. Arguing, therefore, 

 from analogy, we should suppose that the sensation of 

 taste in the lower animals (such as the Crustacea, and 

 other groups in wliich mastication is of an imperfect 

 character), must necessarily be rather a faculty peculiar 

 to the mouth in general, than the result of any especial 

 organ adapted for the purpose. 



From the mouth the oesophagus leads directly to the 

 stomach. The passage is very short, being directed up- 

 wards and forwards; it enters the stomach at the infero- 

 anterior margin, and, as in all Crustacea, is within the 

 limit of the cephalic region. 



Just within the anterior opening of the stomach are 

 situated two rake-like organs, the teeth being placed in 

 a row on an arched base ; they are slightly curved and 

 dentated on the margins. They are so placed as to have 



