This fine nudibranch—the giant of its tribe —is stated by Diquemare, to reach the length
of eight inches; and Sir J. G. Dalyell has found it of similar size, but it is seldom met with
of a greater Jength than six inches, and usually it does not exceed four. It is a deep-water
species, very generally diffused, but seldom obtained except by the dredge or trawl;
occasionally, however, it is brought in on the fishermen’s lines. In its young state it is less
plumose and warty than the adult form. The spawn is deposited in the form of a gelatinous
yellowish-white cord, about the thickness of small whip-cord of great length and very much
convoluted. The eggs are disposed in it about five or six abreast, without regular order.
Sir John G. Dalyell gives a detailed account of the spawning of this animal, in the second
volume o f * The Powers of the Creator displayed in the Creation,’ page 275. In reading it,
however, it will be necessary to bear in mind that the author confounds two species, and that
the smaller masses of spawn figured probably belong to Tritonia plebeia.
Professor Edward Forbes mentions two varieties on the coast of the Isle of Man,—a
purple and a yellowish variety,— the latter is generally longer than the former (often six inches
long) and has the branchiae smaller. The Tritonia atrofusca of Macgillivray was described
from a very dark variety of this species, examined in a dead state. The specimen is in our
possession, having been obligingly presented to us, along with his other Aberdeenshire
Nudi branchiata, by Dr. Macgillivray. His genus Sphterostoma is also founded upon a specimen
of T. Hombergii, in a bad state, as has been before mentioned.
Tritonia Hombergii is very sluggish in its movements, and is not easily kept in confinement.
It discharges a great quantity of mucus. As might be inferred from its immense
jaws, it is a very voracious animal. M. Bouchard Chantereaux states that its principal food
is the Alcyonium digitatum, which is confirmed by the observations of Sir J. G. Dalyell. The
former naturalist has also frequently found individuals between the valves of oysters, of
which they had partially devoured the animal. We have taken from the digestive cavity of
this animal large lumps of the tube of Ampbitrite ventilabrum, with the Alcyonium adhering
to it.
The range of Tritonia Hombergii is nearly co-extensive with the Atlantic shores of
Europe, but it does not appear to reach into the Mediterranean.
Figs. 1, 2, Side and back views of Tritonia Hombergii.
3, Under side of the anterior portion of the same.
4, A portion of the cloak enlarged.
5, A few of the tubercles in profile.
6, A portion of a branchial plume.
7, A tentacle.