thickly covered with flattish, spiculose, unequal tubercles, the smaller ones being very
numerous and much less than the others : it extends considerably beyond the foot, and has
the margins rather thickish; the under side is smooth. Dorsal tantacles slightly conical,
yellow, and strongly laminated above, smooth, transparent, and nearly colourless below.
The laminae are upwards of twenty, alternately large and small; the latter not extending
so far forwards as the former. Branchial 'plumes nine, tripinnate, recurved, large and spreading;
much undulated in outline, and forming an incomplete circle round the anus, open behind.
They are transparent, obscure white, with a purple or lilac tinge at the edges, faintly freckled,
and can be completely retracted within a cavity, the margins of which close over them.
Head rather small, with two small tubercular oral tentacles. Foot broadish, rounded and
grooved in front, less broadly rounded behind, and of a lemon-yellow or orange colour,
with the liver appearing through the centre.
Sjpicula numerous, rather small in proportion to the size of the animal, fusiform, bent in
the centre, and bluntly pointed at the ends, rarely with the surface slightly nodulous: those
in the tubercles are small and more irregularly bent than the others. The heart pulsates
about twenty-eight times in a minute.
Doris tuberculata is a well-known species, common on all parts of the British coast;
and though not so plentiful as some of the smaller kinds, it is, on account of its conspicuous
size, much more readily observed, and is often the only Nudibranch with which the casual
visitors of our sea-coasts are acquainted. It is generally found among rocks about half-tide
level, and from thence down to low-water mark. Its favorite resort is- within the crevices
or under the shelving portions of rocks, hung with small sea-weeds and zoophytes, and
incrusted with sponges, on which it feeds. In such places its very beautiful spawn may
frequently be observed in the spring or early summer, suspended in an inverted cup- or vase-
form, winding into a spiral of about three volutions, with the margins slightly waved. It
consists of a broad gelatinous riband attached by one of its edges. When uncoiled, we have
found it to measure as much as nine inches in length and nearly an inch in breadth. The
ova are placed in transverse lines united in pairs, and amount to about fifty thousand in one
mass of spawn. More than one of these masses are generally deposited by the same
individual in a season. M. Bouchard Chantereaux has found his Doris argus, which is
probably a variety of this species, to produce a coil of spawn of twelve inches in length, and
he reckons the eggs at eighty thousand. Dr. Johnston met with the spawn of Doris tuberculata
winding round the stem of a tangle in a spiral frill, and Sir J. G. Dalyell figures a similar
elongated spiral, evidently the spawn of this species.
This is a very sluggish animal, seldom changing place when kept in confinement, and
crawling very slowly. In its contracted state, as it is usually seen amongst the rocks, it
is an unshapely and unattractive animal, being frequently cramped up to suit the inequalities
of the surface to which it adheres, and to which it holds so tightly that much force is
required to remove it. When placed in a vase of sea-water, however, and its plumes allowed
to expand, it is by on means devoid of beauty.
The range of this species is rather uncertain, as the synonyms of continental authors
cannot be relied upon. It appears to be equally common on the northern and western shores
of France as with us, but we have no decided evidence of its occurrence in the Mediterranean,
as the species called Doris tuberculata by authors describing the productions of that sea is
DORIS TUBERCULATA.
distinct from ours. We think that the Doris tuberculata of Loven, found on the Norwegian
shores, is also probably distinct, though very nearly allied to our species.
Figs. 1, 2. Side and back views of Doris tuberculata.
3. Anterior portion of the underside.
4. Side view of tentacle.
5. Enlarged view of portion of a branchial plume.
6. A portion of the mantle enlarged, showing the tubercles.
7. Spawn.
8. A portion of the same enlarged, showing imbedded ova.
9. One of the ova much enlarged :—a, yolk; b, corion.
10, 11, 12, 13, 14, 15. Embryos, showing progressive development:—b, corion; c, shell;
d, operculum; e, foot; f oral lobes; g, mouth; h, stomach; i, intestine; j , liver;
k, reproductive organs; l, otolithes; m, membranous envelope; n, muscle attaching the
embryo to the shell.
16. Spicula from the cloak.