HABITS OF THE SHIP-WOEMS. 705 



reddish-brown. At the anterior end of the body, and farthest from the external opening of the 

 hole, is seen the small but elegantly sculptured white bivalve shell. The shell covers the mouth 

 and palpi, liver, foot, and other important organs. The foot is a short, stout, muscula,r organ, 

 broadly truncate or rounded at the end, and appears to be the organ by means of which the 

 excavation of the burrow is effected. The shell is covered by a delicate epidermis, and probably 

 does not assist in rasping off the wood, as many have supposed. The gills are long and narrow, 

 inclosed mostly in the naked part of the body, and are reddish-brown in color. 



'< The Teredos obtain their microscopic food in the same manner as other bivalve mollusks, viz, 

 by means of a current of water constantly drawn into the branchial tube by the action of vibrating 

 ciha within ; the infusoria and other minute organisms are thus carried along to the mouth at the 

 other end, while the gills are supplied with oxygen by the same current; the return current 

 passing out of the dorsal tube removes the waste water from the gills, together with the faeces 

 and excretions of the animal, and also the particles of wood which have been removed by the 

 excavating process. 



"As the animal grows larger the burrows are deepened, the lining of shelly matter increases 

 in length and thickness, the shell itself and the pallets increase in size, and the terminal tubes 

 grow longer. But as the orifices of the terminal tubes must necessarily be kept at the external 

 opening of the burrow, the muscular collar at the base of the tubes constantly recedes from the 

 entrance, and with it the pallets ; at the same time imbricated layers of shelly matter are usually 

 deposited in the upper end of the shelly tube, which are supposed to aid the pallets in closing the 

 aperture when the tubes are withdrawn. When the animal has completed its growth, or when it 

 has encountered the tubes of its companions and cannot i)ass them, or when it approaches the 

 exterior of a thin piece of wood and cannot turn aside, it forms a rounded or cup-shaped layer 

 of shelly matter, continuous with the lining of the tubes and closing up the burrow in front of 

 its shell. Sometimes it retreats and forms a second partition of the same kind. 



"This species produces its young in May and probably through the greater part or all of the 

 summer. The eggs are exceedingly numerous, probably amounting to millions, and they are 

 retained in the gill-cavity, where they are fertilized and undergo the first stages of their develop- 

 ment. The embrj-os pass through several curious phases during their growth. In one of the 

 early stages they are covered with fine vibrating cilia, by means of which they can swim like 

 ciliated infusoria; later they lose these cilia and develop a rudimentary bivalve shell, which is at 

 first heart-shaped, and the mantle begins to apjjear and larger retractile cilia develop upon its 

 edge, which serve as organs for swimming ; but at this period the shell is large enough to cover 

 the whole body when contracted. In this stage they swim actively about in the water; later the 

 cilia become larger, a long, narrow, ligulate foot is developed, by means of which they can creep 

 about and attach themselves temporarily to solid objects ; the shells become rounder, a pair of 

 eyes aad organs of hearing are developed. After this the little animal begins to elongate, the 

 locomotive cilia are lost, the eyes disappear, and the mature form is gradually assumed. These 

 young Teredos, when they finally locate upon the surface of wood-work and begin to make their 

 burrows, are not larger than the head of a pin, and consequently their holes are at first very 

 minute, but owing to their rapid growth the holes quickly become larger and deeper." ^ 



This species is very abundant along the southern coast of New England, from Xew York to 

 Cape Cod, wherever submerged wood-work, sunken wrecks, timber buoys, or floating pieces of 

 drift wood occur. It also infests the bottoms of vessels not protected by sheathing. At Province- 

 town, Cajie Cod, about forty feet of the end of the steamboat wharf was so weakened by its 



' Eeport, U. S. Fish Commission, part i, 1873, pp. 384-386. 

 45 F 



