1892-93-] The SJupworm. 67 



shelly lining of the burrow secreted by it. Anteriorly this 

 portion contains part of the body proper ; posteriorly it forms 

 a tube, divided internally by a horizontal partition into two 

 chambers. In the lower chamber are the elongated gill plates, 

 which appear like brown cords. The heart is above the intes- 

 tine, and not perforated by it. In the upper chamber is the 

 rectum. A thick muscular ring terminates this region, and 

 bears two calcareous spoon-shaped plates, closely resembling 

 tennis rackets. The expanded parts of these plates or " pallets " 

 are free, and project backwards, and the handle is fixed in a 

 deep socket lined by epidermis. Behind the pallets the body 

 bifurcates, forming two siphons, which can be contracted or 

 expanded within wide limits of length, and having the orifices 

 fringed. By this contrivance a fresh supply of water for 

 respiration, and its dismissal when no longer fit for use, with 

 the indigestible portion of its food, are efficiently provided for. 

 The function of the pallets is to form a lid as protection to 

 the retracted siphons. They present a feature of much im- 

 portance, so far as specific distinction is concerned. 



Some writers on Mollusca consider the Teredo dioecious, 

 others as hermaphrodite. As in the oyster, the ova are 

 retained in the branchial chamber during the earlier stage 

 of development ; but from the time they swarm and lead a 

 free-swimming existence, to the time when they fasten them- 

 selves to a piece of timber and commence to bore, little as yet 

 is known. Spawning takes place in the spring and summer, 

 and before the end of the year they have reached the adult 

 stage, and their burrows are of large size. How long they live 

 is not known, but it is asserted that they nearly all perish in 

 the spring. That this cannot be the case may be argued from 

 the fact that their burrows are so different in size. 



There is one point upon which I should like some informa- 

 tion — viz., Does an adult Teredo ever manage to leave its bore 

 and seek another piece of timber, or does it die in it ? My 

 own opinion is that it dies in its burrow. In support of this 

 opinion, I have not seen any entrance bores but what have 

 been those of the very young animal, and I cannot imagine a 

 more helpless creature than a Teredo out of its burrow, a cer- 

 tain prey to enemies of every kind. 



The species which occurs chiefly on the west coast of Great 



