FIONA.
inner side of each papilla. The anus is placed about half way down the back towards
the right side. The orifices of the generative organs are separate, placed near together
below the tentacles on the right side.
The anatomy of this animal amply proves its generic distinctness. The tissues are very
tough and firm when compared with the other Eolidida, particularly the skin and the
cellular tissue uniting the viscera. The branchial papillae, too, are much more firmly attached
than usual, and require considerable force to remove them.
The oral orifice is situated on the inferior surface of the head: it is small, and the
external lip is divided behind on the median line, much as in Eolis. The channel leading to
the buccal apparatus is very short and constricted. The buccal mass, (PI. 38a, fig. 4a, and
fig. 5), *is small, rather long, slender, and irregularly elliptical, the corneous plates (fig. 5c)
being visible at the sides: it is slightly prolonged behind, for the reception of the posterior
portion of the tongue, and the muscles are arranged as in Eolis.
The tongue is supported on a fleshy ridge that rises up from the floor of the buccal
cavity, and extends in the antero-posterior direction from the oesophagus towards the anterior
opening. This organ is long, linear, and strap-formed, and is , composed of forty transverse
semicircular plates of an orange.colour, each (fig. 9) bearing a stoutish central spine and six
or seven smaller ones at the sides.. All the spines are a little bent,.and have .their points
directed backwards towards the oesophageal opening.
The corneous plates (fig. 6) .are little short , of the;size of the buccal mass, and much
elongated, well arched and ovate; and, when united and entirely isolated, strongly resemble
the valves of a minute Mytilus. They are smooth, glossy, and of a brownish amber - colour,
darkest towards the anterior extremity, which gives support to the cutting blade (a). This
is a wing-like appendage, of no great size, terminating .below.in a free point, .and having the
cutting margin arched forward, plain, and nearly at right angles to the general direction of
the plate ; above is a small process or fulcrum (3),.the point at which the two plates are
articulated; and immediately behind this point the dorsal margin of the,plates is reflected and
expanded-into an arched lobe (<?), for muscular attachment.
The oesophagus, (fig. 4, 6), is a short and rather slender tube, which, passing from,the
upper aspect. of the buccal mass towards its posterior extremity, opens into the anterior
margin of a distinct pyriform stomach (c). This organ has the broad end forward, is placed
above the reproductive apparatus, and lies,quite in.the anterior portion of the visceral cavity.
The internal surface does not appear to be lamellated. The, intestine (d), passes from the
posterior extremity of the stomach, and inclining slightly to the right .side, passes backwards
to the tubular anus, < (fig. 2a), which is placed a little to the right of the median
line of the back, immediately behind the heart. The intestinal tube is rather short, of equal
diameter throughout, and internally plicated longitudinally.
The hepatic apparatus is very peculiar in this animal. The pyloric extremity of the
stomach receives two biliary ducts (fig. 4 e e), one on each, side- of the intestine. These .ducts,
or hepatic canals, are nearly as wide as the intestine, .and, diverging as they leave, the stomach,
very shortly pass into the skin at the sides of the back, where each, opens into a .wide
channel (ƒ ), .that .extends nearly the whole length of the body. The channels receive
numerous branches, which communicate with the glands of the papillae, and as they approach
the lateral expansion at the sides of the body, they appear to be subdivided several times.
The anterior portions of the great hepatic channels are apparently connected with two
folliculated glandular bodies [y g)„ much and irregularly sacculated. These bodies are
united to the skin, one on each side, near the region of the stomach; and probably form the,
inner walls of those portions of the channels. Amidst the cellular tissue at the extremity of
the body, behind the ovary, there is likewise a glandular substance, {h), of a reddish colour,
folliculated and apparently ramified, in connexion with the branches of the hepatic canals
within the skin. These branches, at the posterior portion of the body, probably form a
sort of network of tubes across the dorsal aspect. Such, perhaps, may be inferred from the
appearance they present (/); when the skin of the back is divided down the median line.
The arrangement of the hepatic canals differs from that, which prevails in the Eolidida.
In Eolis, Embletonia, Doto± Dendronotus, Lomanotus, and Antiopa, the principal canals lie free
in the visceral cavity, and in all of them there is a median posterior trunk. In this genus
there is no such trunk; and the canals are almost entirely within the skin. In this respect
Fiona resembles Hermcea, in which the whole of the hepatic ramifications are apparently
connected with the skin, and there are only two principal trunks, which pass down the
sides of the back. It is evident, however, that the digestive system alone sufficiently
distinguishes Fiona from all the above genera, not excepting Hermeea.
The hepatic glands are large, nearly filling the papillae : they are slightly and irregularly
sacculated, with the inner surface of the investing membrane lined with a dark granular
substance; above, this substance is very abundant, forming a dense mass; below, the
membrane in some of the papillae is entirely devoid of it. We have failed to detect any ovate
vesicle like that of Eolis in the apex of the papillae, neither have we been able to determine
whether or not the apex is perforated.
There are two large, much folliculated glands (fig. 8 c), lying beneath the stomach and
extending almost half way down the body. These terminate in front each in a slender duct,
(d, d), which sinks into the fleshy frontal margin of the foot. At first sight, these organs have
the appearance of being connected with the digestive system, and we originally looked upon
them as salivary glands ; but further experience induces us to believe that they are for the
purpose of secreting mucus, which probably passes out in front of the foot, lubricating the
surface over which the animal is moving.*
The reproductive organs are placed further forward than usual, and have two external
orifices (fig. 1 a, b), one placed a little in advance of the other, on the right side of the head,
between and a little below the tentacles. The one in front is for the exsertion of the
untromittent organ, the other is rather small and is common to both the female and
androgynous apparatus. On laying open the dorsal skin, the reproductive organs are found,
as usual, to occupy much of the visceral:cavity, having the stomach and intestine lying above,
and the buccal mass in front. They are formed on the type of those of Eolis. The mucus-
gland (fig. 4, n,n), is exactly of the same form, and the mode of union of the androgynous
parts with the oviduct and testis is the same as in that genus. The only modification of any
interest is in connexion with the testis (/■). We know of no other species in the whole of
the Eolidida, in which it is furnished with a distinct vas deferens. In this respect Fiona
* The so-named salivary glands of Doto fragilis may perhaps prove to be merely mucus-glands of
a similar nature.