290 Mr. Jeffreys on an undescribed Peculiarity in Teredo. 



moved, or the light suddenly obstructed, they did not withdraw 

 their terminal tubes or siphons. The longer (or alimentary and 

 inhalant) tube was in frequent motion, and inflected in various 

 directions, as if in search of food, while a current of water full of 

 animalcula continually passed into it. The shorter (or fsecal 

 and exhalant) tube performed its functions at intervals, expelling 

 the woody pulp by a spasmodic action, and occasionally with- 

 drawing itself, in order the better to effect its purpose, when 

 any stoppage occurred. Each tube was transparent, and fringed 

 with cilia at its orifice. Professor Harting, in his elaborate trea- 

 tise, which has just been published, ( over het Mechanisme van 

 den Troestel/ &c, appears to have mistaken the nature and 

 relative use of these tubes, calling the longer tube the " cloacaal 

 sipho," and the shorter one the " branchiaal sipho." The Tere- 

 dines seemed to prefer the sunny side of the jar ; and they are 

 said to be very sensitive to cold. But the most interesting 

 peculiarity which I witnessed, and to which my attention was 

 directed by Dr. Verloren (although it has not been noticed, so 

 far as I am aware, by any one of the numerous writers on the 

 Teredo), is that each of the tubes is protected or enveloped ex- 

 ternally by a very thin, pellucid, and film-like membrane or 

 sheath. These tube-sheaths are irregularly annular, like the 

 testaceous tube or tunnel which lines the excavation in the 

 wood ; and they bear a considerable resemblance in form to the 

 stem of Tubularia indivisa, though differing from it in texture 

 and colour. The alimentary tube-sheath is about an inch long, 

 and the other is half that length. Their annular structure 

 evidently arises from successive accretions of growth. The use 

 of the sheath in Teredo may be either to prevent the delicate 

 tubes, which it covers for about half their length, being choked 

 or obstructed by the accumulation of flocculent pulp which lies 

 outside, or else to protect them from the attacks of minute pre- 

 daceous animals. It is renewed from time to time ; and in one 

 of the specimens four separate sheaths were attached to the 

 tubular opening in the wood, one pair having been apparently 

 disused, and a new set formed for present use. I am more than 

 ever of opinion that the foot of Teredo (and most probably of 

 every other boring shell-fish) is the sole instrument of perfora- 

 tion, instead of any of the methods described in the ' History of 

 British Mollusca.' 



I will add a few words as to the synonymy of Teredo marina. 

 The Teredo navalis of Linnseus comprised at least two species 

 (viz. T. Norvagica, or the " Italianische see-wurm w of the older 

 Dutch writers, and T. marina of Scllius), as appears from the 

 references in the twelfth edition of the ' Systema Naturae ' to 

 Vallisnieri, Plancus, and Sellius. The diagnosis (" Teredo intra 



