134 The Teredo, or Shipworm. [February, 
the shelly lining of the Teredo’s gallery or burrow into countless 
_ pieces. 
These burrows vary from one quarter of an inch or less to half 
an inch or more in diameter. 
It is only in its very earliest stages that the Teredo is a free 
moving animal. At this time no one other than a practiced nat- 
uralist would be likely to recognize it. “It is very minute, nearly 
spherical, and covered with cilia or hair-like projections, by means 
of which it swims rapidly through the water. In thirty-six hours 
it assumes a new form, and speedily changes it for another, after 
which it returns again to its original form, so that in a very few 
hours the little creature is first spherical, then oval, then triangu- 
lar, and then spherical again. In this stage of existence it pos- 
sesses a foot which enables it to crawl after the manner of snails, 
and also has organs of hearing and sight.” 
It does not enjoy its locomotive powers for any long time but 
fixes itself to some suitable object, passes through its last change, 
becomes a veritable shipworm and begins its lifelong task of 
boring. 
The Teredo is not very particular as to the kind of timber into 
which it bores, but always goes with the grain, unless it meets 
with some obstacle, such as a nail or a very hard knot; and in 
such a case it turns out of its track for a short distance and then 
resumes its former course. As it bores its way along, it lines the 
tunnel (as before stated) with a coating of shelly matter, but this 
is not attached or in any way connected with the body or sub- 
stance of the shipworm. 
It is not believéd that the wood it perforates furnishes any - 
nutriment to the animal, but that its sustenance is derived entirely 
from the water which is constantly passing through its body. 
The holes made in the wood at the time or just after the young 
Teredos commence burrowing are quite small, the appearance of 
the surface of a pile or other infested timber is usually deceptive, 
affording but little evidence of the size or number of the burrows - 
or the extent of the ravages within. After awhile the interior is 
so completely “honeycombed” that a slight blow or bump by 4 
vessel upon the outside shatters the pile, &c., and their damaging 
work can be seen. 
` Upon the water front of San Francisco I have known piles, of 
Oregon pine and fir over a foot in diameter, rendered worthless in 
