S96 Dr Coldstream on the Structure and 



Locomotion is performed by creeping and swimming. It 

 creeps very slowly, backwards as well as forwards, and seems to 

 drag itself along. But it swims rapidly, using chiefly the caudal 

 lamellae, which it moves in the manner of oars. Sometimes also 

 it propels itself, by a sudden movement of its tail, backwards, to 

 the distance of an inch or two, through the water. When taken 

 out of the water, and laid upon its back, it cannot right itself. 

 It often swims in circles, with the head directed downwards, and 

 sometimes it narrows these circles so much that it seems to wheel 

 round upon its head as a centre. 



In considering the digestive function, we are naturally led to 

 inquire, 1. What is the nature of the animal's food ? 2. How 

 is the food procured ? and, 3. How is it prepared for being re- 

 ceived into the internal digestive tube ? With regard to the 

 first point, — the nature, namely, of the Limnoria's food, — it ap- 

 pears to me to be sufficiently established, that the animal feeds 

 upon the wood through which it bores, and that from the fol- 

 lowing circumstances : Firsts That no woody particles are seen 

 to float out from the hole when the animal is engaged in boring 

 under the eye pf an observer, the side of the hole being cut away 

 to obtain the view : Secondly/, That I have never seen it attack 

 any other substance with its mandibles. Thirdly, That the 

 contents of the stomach resemble comminuted wood. 



It would seem, therefore, that the Limnoria furnishes an ex- 

 ception to the general proposition, stated by many naturalists, 

 — that all the Crustacea feed on animal substances. 



Many kinds of wood are devoured by the Limnoria. On 

 this coast, it is generally in fir-timbers that it is found. But at 

 the Bell-Rock, Mr Stevenson saw it attack oak, black birch, 

 and other woods ,* and indeed, teak was the only wood exposed 

 to its ravages that was not perforated. I am not aware of any 

 fact proving that the Limnoria attacks floating timber. It seems 

 to attach itself in preference to wood fixed on the sea-shore. And 

 it is of importance to remark, that it often effects a lodgement in 

 piles, very near high water-mark, where it is left dry by the re- 

 ceding tide during the greater part of the twenty-four hours. I 

 see no reason, however, why it should not attack floating timber, 

 not covered by something impervious to its mandibles. Our 

 coasting vessels are generally sufficiently protected from its at- 



