Dr. W. C. M‘Intosh on the Boring of certain Annelids. 281 
it is not the helpless animal described by Dr. Johnston*, but 
progresses very actively indeed, either on a horizontal or per- 
pendicular surface; and if circumstances are unfavourable for 
its gaining the stone, or, if it so chooses, it fashions a tube 
round its body with ease and rapidity (provided materials are 
forthcoming), either on the bottom or along the side of the 
vessel. Nor is it satisfied with the construction of one home, 
but roams about from place to place and forms several. In 
such instances the tube is not generally turned on itself, 
but is more or less linear, the cup of the anal segment com- 
municating freely with the water by the open end of the tube. 
They are also not unfrequently found swimming on the sur- 
face of the water, like other Annelids. 
The first point that strikes the observer in regard to the 
perforations in the sandstone and shale is that they are grouped 
im pairs, sometimes with a thicker and sometimes with a 
thinner intervening column. In many cases this column would 
seem to be formed of débris ; but in others, especially those in 
shell, sandstone, and Corallina, some of the original material is 
left; so that, by this feature, the observer is seldom left in 
doubt as to the identity of any particular gallery he encounters. 
From the exterior the tubes, as usually observed, proceed in- 
wards either as nearly straight or more or less curved cylin- 
drical galleries, and terminate in the case of each pair by 
joining in a loop at the bottom, the latter being either abruptly 
or gently curved, according to the thickness of the intervening 
column. This siphonal form of gallery is very general among 
the Annelida and other burrowing animals; various Terebella, 
Eunice sanguinea, Cirratulus cirratus, and others follow this 
habit in the fissures of rocks; while Corophium longicorne, so 
abundant in company with Hdwardsia on some of our muddy 
or clayey shores, has its burrow of the same characteristic 
formation. In Leucodore, as a rule, the intervening column 
attains the largest dimensions inferiorly, a considerable wedge of 
sound shale being often left at the loop. The latter, moreover, 
in some was marked by two or three grooves, showing that at 
various times the animal had altered the depth of its galleries 
to suit its convenience, perhaps in relation to the length of its 
built-up or external tube, though this is not a matter of much 
consequence. All the tubes were lined by the delicate secre- 
tion before mentioned. 
In the borings in shell, Nullipore, and Corallina the tube or 
perforation had not, in our specimens, the form of a keyhole, 
as mentioned by Mr. Lankester, but possessed a solid column 
of the original structure, or else one of consolidated débris, in- 
tervening between the tunnels. In the sea-worn specimens of 
* Catalogue of Worms, Brit, Mus. p. 206, 
