Behavior of Tubscolous Annelids 161 
ing surf are constantly imposing upon objects under these con- 
ditions. ‘The tubes show throughout the closest adherence to the 
rocks, which in this environment forms the almost exclusive base 
of support, though one sometimes finds specimens attached to the 
shells of living snails occupying these pools. When in the process 
of growth the worm comes to a sharp angle of the rock it either 
turns and grows back upon itself, or turns sharply over the edge 
and along the opposite surface. In these conditions the tubes 
show a distinctly flattened surface along the line of contact which 
is hardly perceptible on those from deeper waters. All these 
facts lend still further confirmation of the suggestion of adaptation 
as the more probable explanations of the facts, rather than the 
more usual explanation of stereotropism, though the latter may 
not be wholly lacking. 
As already intimated in the beginning, pains were taken to 
secure specimens from as wide a range of depth and habitat as 
possible in order to detect any peculiarity of behavior which might 
be due to purely local, or environmental conditions. From result- 
ing comparisons marked differences were distinguishable in speci- 
mens dredged from a muddy bottom and those from rocky or 
sandy bottoms. ‘The former tended to grow in larger colonies, 
and in a more or less vertical aspect, while the latter were often 
isolated and independent, and closely adherent throughout to the 
substratum, as much asthose to be found intide pools or shore lines, 
referred to above. ‘The extreme contrast was found in colonies 
taken from the debris about river mouths, or enclosed bays which 
received the drainage or sewage of adjacent towns. In these con- 
ditions colonies of immense size were found, made up of hundreds, 
or even thousands, of specimens. In some cases these aggregations 
were apparently of considerable age and formed massive calca- 
reous accumulations, not greatly unlike coral heads in sub-trop- 
ical harbors. Ocgasionally colonies would be found on the most 
unexpected substratum. For example, the writer was shown one 
such taken by Mr. Geo. M. Gray at the mouth of the New Bedford 
river growing on an old granite kettle, covering it almost com- 
pletely, both inside and out, and forming a most picturesque 
object, especially when the hundreds of specimens of various size 
