86 Trans, Acad. Sci. of St. Louis 
growth. Since it was not possible for them to increase 
the length or diameter of the tube or the size of the shell, 
the only noticeable activity was in the regular addition 
of denticulate ridges and an increase in the thickness 
of the shell, this peculiar growth rendering them almost 
unrecognizable. In view of the fact that the shipworm 
is supposed to be able to obtain more or less nutriment 
from the wood into which it bores (Dore and Miller, 
1923), (Harrington, 1921), it is interesting to note that 
the stenomorphic specimen, at least, is not dependent 
upon the wood for food, for living specimens of steno- 
morphic Teredo navalis have been found with a total 
tube length of only ten millimeters and yet with a known 
age of ten months. A normal Teredo navalis during the 
active season, will form a ten-millimeter tube in less 
than two weeks time. That the animal of the steno- 
morph should continue to produce denticulate ridges 
when there is no more available wood upon which the 
denticles can be used, is even more interesting. 
I wish to express my appreciation for the assistance 
which has been given to me in my study of the shipworms 
at the Massachusetts Institute of Technology, through 
the kindness of Professor Samuel C. Presscott. Ex- 
cellent laboratory facilities, photographic apparatus, 
etc., have been freely placed at my disposal. 
I am also indebted to Mr. Nelson M. Fuller for the 
excellent photographs and for other assistance in my 
work. 
