TEREDO. 135 



the oyster and other shell-fish, and is derived from the 

 kind of wood in which it lives. I can answer for its 

 being very disgusting and almost insupportable. The 

 valves of the shell found in fir- and alder-wood are 

 white, almost pearly, and marked with pale ash-coloured 

 strise and dots; Avhereas those taken out of oak are almost 

 entirely yellow, sometimes of the darkest shade of black 

 with strise and dots of the latter hue. This remark 

 applies to the external surface only, and not to the 

 inside, which is uniformly pure white and pearly. The 

 pallets or '' pinnae '' have a yellowish tint, and their stalks 

 are invariably of the same colour and lustre as the inside 

 of the valves. The colour of the sheath varies in like 

 manner according to the kind of wood. The outside tints 

 appear to be extraneous, and not inherent in the Teredo 

 or secreted by it. Rousset having succeeded in keeping 

 Teredines alive in his own house, Sellius thought that 

 oysters, mussels, and other kinds of eatable testacea might 

 be profitably cultivated in tanks or reservoirs. A small 

 crustacean, called " Springertje " or '' Snel '^ {Limnoria 

 lignorum, Rathke), is generally seen in company with the 

 Teredo, and with its horny mandibles gnaws away the sur- 

 face of the wood. With regard to the mode of perforation 

 by Teredo, I have already stated the views of Sellius in the 

 ^ Introduction ' to the first volume of the present work. 

 I would, however, add that I am now inclined to difier 

 from him in the supposition that the adult shell is not 

 strong enough or adapted to rasp the wood. Cailliaud 

 has shown practically that this can be done ; and I have 

 lately repeated, with success, the same experiment. But 

 the improbability of the young or newly born shell being 

 able to effect a lodgment in this way seems to me as 

 great as ever. By examining the Teredo in situ, it will 

 be manifest that the foot is closely applied to the larger 



