540 CRUSTACEA. 



narrow orifice of the mouth ; which seems to be furnished with 

 vibratile cilia, that serve to draw into it the semi-fluid aliment. 

 Instead of being furnished (as in the higher Crustaceans) with 

 two pairs of antennae and numerous pairs of " feet-jaws," it has 

 but a single pair of either; it also bears four minute ocelli, or 



FIG. 275. 



Ammothea pycnogonoides : a, narrow oesophagus; 6, stomach; c, intestine; d, digestive caeca of the 

 feet-jaws ; e, e, digestive cseca of the legs. 



rudimentary eyes, set at a little distance from each other on a 

 sort of tubercle. From the thorax proceed four pairs of legs, 

 each composed of several joints, and terminated by a hooked 

 claw ; and by these members the. animal drags itself slowly along, 

 instead of walking actively upon them like a crab. The mouth 

 leads to a very narrow oesophagus (a), which passes back to the 

 central stomach (5), situated in the midst of the thorax, from the 

 hinder end of which a narrow intestine (c) passes off, to terminate 

 at the posterior extremity of the body. From the central stomach, 

 five pairs of caecal prolongations radiate ; one pair (d) entering 

 the feet-jaws, the other four (e, e) penetrating the legs, and pass- 

 ing along them as far as the last joint but one ; and these exten- 

 sions are covered with a layer of brownish-yellow granules, which 

 are probably to be regarded as a diffused and rudimentary con- 

 dition of the liver. The stomach and its ceecal prolongations are 

 continually executing peristaltic movements of a very curious 

 kind ; for they contract and dilate with an irregular alternation, 

 so that a flux and reflux of their contents is constantly taking 

 place between the central portion and its radiating extensions, 

 and between one of these extensions and another. The space 



