1888-89.] The Duke of Argyll on Bodies of Organic Origin. 57 
its walls ; whilst, on cutting away the sand, that path becomes 
visible in a solid plaster-of-paris cast. The combined result of 
those experiments is to show how worm tubes would he deformed 
by movements in the bedding of the rocks, sometimes producing 
simply a change from circular to ovate forms, but in the case of 
more extensive movements, leading to flattened and broadened shapes 
and impressions, which must be more or less difficult of interpreta- 
tion, because more or less widely divergent from original and undis- 
torted tubing. Another most interesting result of this examination 
has been an ocular demonstration of the fact that the worm path 
is marked by a distinct development of iron oxide for some little 
distance on every side of the tube. The sand, in this case is much 
mixed with clay, and is of a dark bluish-black colour. A ferru- 
ginous band is produced in this substance round the tube. This 
ferruginous hand varies, as we might expect it to do, in width 
according to the quantity of iron in the sand, and according to the 
length of time during which contact with the animal matter has 
been maintained. Means have been found of hardening the sand 
so as to preserve these instructive specimens, and I now lay before 
the Society several of them, one being a specimen in which the worm 
is exposed lying dead in his burrow-tube, and the ferruginous stain 
is seen spreading to a very considerable distance on either side. 
How this chemical effect results from the proximity of the worm 
is an interesting question. I produce, also, some other specimens 
showing irregularities in the tubes, swellings and contractions, pro- 
duced apparently by the worm turning in its burrow, and crossing 
the path of another worm, or its own, all tending to explain how 
there must he many obscure marks left in rocks in the original 
material of which such worms have burrowed. I produce speci- 
mens also, which exhibit beautifully the segregation of finer material 
along the path of the worm, precisely as we should expect from the 
functions which that animal fulfils in swallowing and in discharging 
the substances through which it works its way. Every anticipation 
which can he suggested by reasoning and by inference is found to 
be fulfilled in the observed results. 
Standing then upon this series of facts connected with living 
annelids, we have solid grounds for defining a whole group of 
characteristics which must belong to the traces or remains of 
