ZOOLOGY. 359 



sions, but have a principle over which there should be no possibility of dis- 

 cussion. 



INVESTIGATIONS RELATIVE TO THE TEREDO OR SHIP-WORM IX 



AMERICAN WATERS. 



The following is an abstract of a paper recently read before the National 

 Institute at Washington, by James Jarvis, Esq., who has been engaged since 

 1849 in a series of experiments concerning the Teredo, or ship- worm, by order 

 of the Bureau of Yards and Docks. In order to ascertain the best composition 

 for resisting the attacks of the teredo upon wood he painted a number of 

 blocks and boxes with various compounds some he left unprepared, and some 

 partly painted and sunk them in Elizabeth river at Norfolk, Ya., in the 

 month of April. 



I commence about the twelfth of June to examine the blocks and boxes. 

 I have never been able to discover any of the animalcula until about the 20th 

 of June. The examination takes place as follows : The blocks and boxes are 

 taken from their locations and wiped clean and dry of the fucus and barnacle. 

 After a strict examination, and seeing no orifice, I apply a magnifying glass, 

 with which I run over the surface ; no hole appearing where a minute animal 

 might have entered, I take a fine shaving off the surface, and then apply the 

 glass again. About the 20th of June, annually, I begin to discover a minute 

 hole ; I then cut around the orifice, and see a very small white bulb of almost 

 invisible matter. I remove the atom by lifting it on the point of a fine 

 needle, and place the object under the microscope, where I see developed the 

 Teredo, the Salt-water Worm, perfect in ah 1 its parts, and capable of cutting 

 wood for its subsistence. As soon as the shell-fish is discovered, the crust 

 which protects the animal can be also seen formed around it. Daily the animal 

 continues to grow ahead I say grow ahead, for these creatures have no loco- 

 motive powers ; they have neither arms, legs, nor fins, but grow like an 

 oyster ; they are a gelatinous substance ; their habitations are only in wood. 

 As they grow, they manufacture a calcareous sheathing adherent to the sur- 

 face of the burrow. The animal grows as that envelope of lime increases in 

 size ; but at all times the shell-fish seems to fill the latter. During the sum- 

 mer they grow from six to twelve inches in length, and generally to about 

 three-eighths of an inch at most in diameter, at Norfolk harbor. The worm 

 excavates a tunnel equal to twelve inches in length and three-eighths of an 

 inch in diameter; the wood excavated would be more than a cubic inch, if in 

 a solid piece. The body of the worm and its shelly envelope, if in a solid, 

 would not be half its contents. What becomes of the wood excavated ? 



I continue to place the blocks in the river until after frost ; I have never 

 (so far) discovered any sign of the shell-fish in any of the pieces of wood 

 deposited after the 29th of September. It may be relied on as to the harbor 

 of Norfolk, and I suppose of the Chesapeake Bay and its tributaries, up stream 

 as far as the water is sufficiently salt, that the salt-water worm does not hatch 

 before the 20th of June of each year, and that they do not enter after the 

 30th of September of each year. The shell-fish being hatched before the 30th 

 of September will continue to do damage until the cold weather destroys 



