between the cloak and the foot in front, and is furnished with two oral tentacles, very variable
in shape, sometimes linear, sometimes tubercular or flattened, and sometimes their place is
supplied by a veil, which surrounds the head, and may be considered a modification of these
organs. The mouth is occasionally slightly protuberant ; it is most commonly without jaiys,
but sometimes very rudimentary ones exist; and it is frequently furnished with a spinous
prehensile collar at the buccal orifice. The tongue is denticulated. Doris was long supposed
to be without eyes. Those organs, however, are always present; but in most cases must
perform the function of vision very imperfectly, as they are seldom to be seen through the
skin excepting in some very transparent species, or in very young individuals. There are
two dorsal tentacles, which are placed on the cloak in front, and at some little distance from
the margin; their form is generally linear or clavate, the upper portion being always
laminated ; they are retractile within cavities, the margins of which are sometimes produced
into short sheaths. The branchiae are plumose and surround the anus, which is situated
posteriorly on the central line of the back. They consist of several plumes, sometimes small
and simple, sometimes large, and more or less branched ; and are either united at the base
into a flower-like expansion, or placed separately in a circle, more or less broken posteriorly.
In the typical division of the genus, these plumes are retractile within a common cavity, the
margin of which is capable of being closed completely over them, so as to protect them from
danger. In those abnormal species that form our second and third sections there is no
cavity; the plumes are consequently not retractile, but contractile only, being, in their
contracted state, curled up, and drawn closely down on the surface of the cloak. The foot is
flat disc of an oblong form. The aperture of the sexual organs is single, and situated anteriorly
on the right side between the cloak and the foot.
We are inclined to believe that the Dorides are carnivorous; but this fact has not been
sufficiently investigated. D. tuberculata has been detected feeding on Hcdichondriapanicea,
and Grantia compressa, and the stomach of this species is almost always found filled with
fragments of the former sponge. It is likewise worthy of remark, that D. depressa, D. sparse
and D. inconspicua are found adhering to calcareous zoophytes, on which there can be little
doubt that they feed.
This genus has a wide geographical range, species occurring from the frozen to the
torrid zones, and in every quarter of the globe. In depth it extends from the littoral to the
coralline zone; but is most abundant in the littoral and laminarian. Some species are found
equally abundant in both these zones; and in particular D. pilosa may be mentioned. This
species has a peculiar structure within the stem of the branchial leaflet highly developed,
giving the cha acteristic star-like appearance in the centre of the branchial circle. The
structure just alluded to is also found in D. tubercidata. It is composed of a series of irregular
cells with thickish elastic walls, and is apparently intended to give reciliency to the branchial
plumes, keeping them to some extent expanded, even when out of water, and thus, perhaps,
certain species may be enabled to extend their range to within tidal marks.
Ehrenberg made an attempt at a redivision of this genus in his | Symbol» Physic»,’
published in 1831; his arrangement, however, does not include the whole of the forms
contained in the genus, but appears to be confined to the species that had come under his
observation. He restricts the genus to those species (not otherwise distinguished) which have
the branchi» retractile within a cavity, arid divides them into the following sub-genera.
a. Branchiis simpliciter ligulatis. Glossidoris.
b. Branchiis ligulatis, apicibus furcatis, incisisve. Actinodoris.
c. Branchiis simpliciter radiatis, radiis simpliciter pinnatis. Pterodoris.
d. Branchiis radiatis, ramosis, compositis, fructiculosis. Dendrodoris.
He also describes four new genera founded upon foreign species, some of them rare, and
still remaining unfigured. His sub-genera, it will be observed, are formed from the character
and mode of branching of the branchial plumes. We do not think that these will be found
to lead, in all cases, to natural groups: to divide the simply pinnate from those with doubly
pinnate or branched plumes, would occasionally separate species very closely allied; for instance,
no two species are more closely allied than our Doris Johnstoni and Doris coccinea; yet, according
to Ehrenberg’s views, the former would be a Dendrodoris and the latter a Pterodoris.
In our provisional synopsis to the present work, published in 1845, we divided the
British species of Doris into three sections, characterised by the position of the branchi», and
their retractibility into a cavity or otherwise. These divisions, which we still adhere to, are
given below.
But the most extensive subdivision of the Dorides is that of Mr. J. E. Gray, in the1 fourth
volume of Mrs. Gray’s ‘Figures of Molluscous Animals/ published in 1850. In this,
Ehrenberg’s sub-genera are adopted and raised to the rank of genera, with the exception of
Pterodoris, which is left out, and Dendrodoris is divided into two, Dendrodoris and Doris; the
former being restricted to species with the anus behind the branchi», a distinction which we
think will not hold good, as the species therein enumerated have the anus really in the centre
to which the plumes converge, though the circle is incomplete. Our second section, which
Mr. Gray adopts as a genus, he considers to be the Onchidoris of Blainville; the character on
which that naturalist separates his genus from Doris is not, however, to be found in the
animals composing this section. Our third section Mr. Gray forms into a genus under the
name of Acanthodoris. He also adopts the genus Villiersia of D’Orbigny, which we have
ventured to discard for reasons mentioned in our account of Doris depressa. Some other
genera proposed by Mr. Gray, having reference to foreign species only, we shall not at
present stop to consider, more especially as the descriptions of authors are in general so
imperfect, that without some more accurate information concerning structural peculiarities
(independently of colour and markings, which are frequently the only characters given) it
would be impossible to come to any very satisfactory conclusions with regard to the great
mass of species now included in the genus. For this reason, we shall content ourselves
with giving the following groups as sections only, though there can be little doubt that they
will ultimately rank as genera.
Section 1. Branchiae-united at the base, and retractile within a cavity; body more or less
depressed; with oral tentacles. Type, Doris tuberculata.
Section 2. Branchiae set separately in an open circle, non-retractile; without oral tentacles,
their place being supplied by a veil. Type, Doris bilamellata.
* Body not much depressed, with moderately sized spicula; spawn generally of few
coils, and cup-formed. Type, D. bilamellata.
* Body very flat, with large spicula, symmetrically arranged; spawn narrow, of many
coils. Type, D. depressa.
Section 3. Branchiae united at the base, non-retractile; body convex; oral tentacles indistinct,
united into a veil. Type, Doris pilosa.