NATIONAL FISHERY CONGRESS. 191 



Once the shipworm has set into the wood it grows with amazing rapidity in our 

 southern waters. In twelve days it has grown to be an eighth of an inch long, in twenty 

 days about half an inch, and in thirty-six days 4 inches, when it is thousands of times 

 as large in volume as when it sets. It has become sexually mature, and is ready to 

 produce a new generation. How long shipworms may live has never been observed, 

 though it is probable for several years, and that during this time they keep growing if 

 there be room in the wood for growth, though when crowded the individuals become 

 dwarfed. The writer has found specimens of great size of T. norvegica, some 3 to 4 

 feet long, and it is easily seen how destructive may be a few of these individuals 

 which may be almost an inch in diameter. The age of such specimens I have not been 

 able to determine, but it is estimated i/o be less than two years. 



In the colder waters of Long Island the writer has found specimens of both 

 T. navalis (?) and Xylotrya Jimbriata, the former the more abundant. They seem to 

 set most abundantly after the 1st of July, though observations for one season can not 

 be conclusive. The rate of growth is much slower, and it would seem to take twice as 

 long to attain the same sizes as in the warmer southern waters. 



The writer in his studies of shipworms has paid most attention to features purely 

 scientific in their interest. Observations of any considerable economic value must 

 cover a variety of localities under different conditions and extend through a period of 

 years observations which the writer has not had sufficient opportunity to make, and 

 which for our American forms have unfortunately never been made. 



MINNEAPOLIS, MINNESOTA. 



