Notes on the Stenomorphie Form of the Shipworm 85 
millimeter specimens of the same species. Furthermore, 
at the same locality the increase in the size of the test- 
blocks in 1923 to 4x4x6 inches did not change the result 
in the slightest degree, the proportion of stenomorphs 
being as great and the average size of the stenomorphic 
specimens being the same in the large blocks as in the 
small. Also, several of the numerous specimens of piling 
received from various localities on the Atlantic Coast, 
some of which were 18 inches or more in diameter, 
showed the same stenomorph form, not separable from 
those found in the small test-blocks. 
From the above facts it is evident that the size of 
the wood is not necessarily the deciding factor in the 
production of the stenomorphs, for if it were, steno- 
morphs would not occur in large piles where plenty of 
wood remained unoccupied. In a great majority of the 
pieces of wood containing stenomorphic specimens which 
I have examined, I have found that the conditions at the 
time of the attachment to the wood of the embryo, were 
apparently very favorable. Many embryos entered the 
wood at the same time, frequently thirty or forty to 
the square centimeter. A large majority survived, but 
many specimens, owing to the fact that some of their 
neighbors entered the wood slightly earlier, or were 
more active in boring than they, soon found themselves 
unable to advance in any direction, for the reason that 
they were completely surrounded by the tubes of other 
specimens. The shipworm will never break through the 
partition of wood, however thin it may be, which sepa- 
rates it from a neighboring tube, whether the occupant 
of that tube be living or dead. These confined specimens 
continued to live for as long a period as those more 
fortunate individuals which were not checked in their 
