their Food and Digestive Organs. 



223 



38 



i 



shrimp lying in spiall, seeing this good time 

 & opportunitie, giueth token thereof to the 

 Nacre, secretly with a little pinch. She hath 

 no sooner this signall, but she shuts her 

 mouth, & whatsoever was within, crushes 

 & kills it presently; & then she deuides 

 the bootie with the little crab or shrimp, 

 her sentinell and companion. I maruell 

 therefore so much the more at them who 

 are of opinion, that fishes and beasts in 

 the water haue no sense." (Vol. i. p. 261.) 

 Of bivalves there are some which, as I 

 have told you, bore into wood and rocks ; 

 but I need scarcely guard you against en- 

 tertaining the supposition that they eat the 

 material on which they work, although 

 there are authors who have attributed to 

 them " a stone-eating power and appe- 

 tite." The Teredines, however, really eat 

 the wood destroyed by them ; for Mr. Hat- 

 chett proved the pulp in their intestine 

 to be vegetable sawdust ; but I agree with 

 Sir E. Home in thinking that the saw- 

 dust serves only as a substance in which 

 the real food procured from the sea is 

 entangled and prevented from escaping too 

 readily from the stomach. I will give you 

 Sir Everard's description of the digestive 

 organs {Jig. 38.) of these animals, which a 

 comparison will prove to be altogether 

 different from those of the more typical bi- 

 valved Mollusca {Jig. 31.). The oesophagus 

 {Jig. 38.* a) is now very short, and lies 

 on the left side of the neck : the canal 

 swells out, and becomes stomach (Z>), which, 

 in its external appearance, is a large bag, 

 extending the whole length of the cavity 

 of the abdomen, but, when laid open, it is 

 found to have a septum {c) dividing it 



* This figure represents the course of the sto- 

 mach and intestines of T^eredo navalis, removed 

 from the body, a, The oesophagus ; b, the stomach ; 

 c, the septum, dividing it into two cavities ; d, the 

 aperture by which the two cavities of the stomach 

 communicate j e, the course of the intestine to its 

 termination. (Comp. Anat.y t. 80.) 



