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 
animaleula continually passed into it. The shorter (or fecal 
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 Linnzus comprised at least two species 
(viz. T. Norvagica, or the “ Italianische see-wurm ” of the older 
Dutch writers, and 7. marina of Sellius), as appears from the 
references in the twelfth edition of the ‘Systema Nature’ to 
Vallisnieri, Plancus, and Sellius. The diagnosis (“ Teredo intra 
