235 



larger one did not always retract when touched, but upon touching 

 the smaller one, both were instantly drawn in. 



In examining the shell while in the wood, there appeared to be a 

 small portion, nearly at right angles to the cylinder, sufficient only 

 to give a passage to the two small tubes. The shell was found, when 

 analysed by Mr. Hatchett, to be perfectly similar to that of the Te- 

 redo gigantea. 



The largest of these worms was 8 inches in length ; many of them 

 lived 24 hours after separation from the shell ; in these the heart was 

 distinctly seen to palpitate. The blood in the vessels going to the 

 head, and also in the parts near the liver, was of a red colour ; but 

 this colour disappeared soon after death. 



From the middle of the exposed part of the head proceeds a kind 

 of proboscis. As this has no orifice in it, Mr. Home thinks it pro- 

 bable that it adheres to the wood, and acts as a centre-bit, while the 

 animal works with the boring shells, between which it is situated. 

 The mouth is nearly concealed by the projection of this proboscis. 

 The body of the animal terminates in a small double fold, forming a 

 cup, on the inside of which are two opercula, which, when brought 

 together, close up the shell : these opercula do not correspond to the 

 tubes, but are in a contrary direction. Jn the Teredo gigantea the 

 opercula are situated in a similar manner, each shutting up one half 

 of the bifurcation. 



Some other observations, which our limits oblige us to omit, are 

 made on these animals before Mr. Home proceeds to describe their 

 internal structure as observed in the dissection. Here also we must 

 content ourselves with mentioning the most striking circumstances, 

 referring those who wish for more particular information to the paper 

 itself. 



Into the cavity of the worm there are two natural openings ; one 

 of these is the larger tube already described, by which it receives 

 water from the sea ; the other is an aperture under the boring shells, 

 forming a slit in a transverse direction, which opens into the space 

 before the boring shells. 



The breathing organs are attached on the posterior surface of this 

 cavity, and have their fringed edges loose, and exposed to the sea 

 water, which passes through this cavity to the head of the animal. 

 In the worms, which were examined while alive, the stomachs, which 

 extend the whole length of the abdomen, were quite empty ; but in 

 the stomachs of some of the preserved specimens there was found a 

 yellow-coloured pulp, which, from some experiments made on it by 

 Mr. Hatchett, appeared to be an impalpable vegetable saw-dust. 

 The intestine, after various inflections, terminates in the small tube, 

 through which it empties its contents into the sea. 



The heart consists of two auricles, which open into two tubes ; 

 these uniting, form the ventricle. The circulation is, of course, 

 single ; but the mode in which it is performed seems to be peculiar 

 to this animal ; the blood being thrown out from the heart, towards 

 the viscera and the head, and carried afterwards through the ves- 



