NATIONAL FISHERY CONGRESS. 
191 
Once the shipworm has set into the wood it grows with amazing rapidity in our 
southern waters. Intwelvedays 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 to be less than two years. 
In the colder waters of Long Island the writer has found specimens of both 
T. navalis (?) and Xylotrya fimbriata, 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. 
