Trinchese’s paper at the time they wrote. Whatever may be the true affinities of the
form, the differences in the buccal parts prevent its being referred to Galma, and I would
propose that it should be rebaptized Galmella.
Though the anatomy of Galma is characterized by a certain simplicity, this simplicity
is no doubt n.ot primitive, but secondarily acquired and connected with the unusual
diet of the animal, which feeds on the eggs of fish. The nature of the food explains
the degeneration of the radula and perhaps also the absence of cnidocysts (see Grosvenor,
“ On the Nematocysts of AEolids,” Proc. Roy. Soc., 1903,. vol. lxxii, no. 486, p. 469).
Several of my specimens seemed to be gorged and distended with gelatinous matter, and
probably the creatures’ habit of thus stuffing themselves accounts for the breadth and
simplicity of the alimentary passages.
CALMA GLAUCOIDES A.;& H.
Seven specimens received from the Plymouth Laboratory. Two of them resemble
Alder and Hancock’s figures more than do the others, which are flatter and have swollen,
almost ovate cerata. But no differences of structure were found, and as all the specimens
were identified at the Laboratory with G. glaucoides, it is probable that they were all
alike externally when alive.
The length varies from 10 mm.'jto 4 mm. and the breadth from 4 mm. to 2 mm.
The general colour is whitish or drab, but varies in detail, because the transparent
integuments allow the contents both of the body and of the cerata to be seen. The broad
digestive tract with its diverticula is generally coloured a pale dull yellow, but contains
here and there blackish masses in the cerata as well as in the main alimentary tract. In
two specimens these black portions are so large that the general colour appears to be
bluish blaok. At the sides of the body between the cerata the white follicles of the
hermaphrodite gland are distinctly visible. The integuments are generally brownish at
the sides of the body and at the bases of the cerata.
The margin of the foot is expanded both in front and at the sides, so as to be
considerably wider than the head and body; anteriorly the foot is rounded, and is
produced on either side into a short tentacular process, which is almost invisible in many
specimens. The cerata are set in from nine to twelve rows, the most common number
being ten. Each row contains two or three cerata, more rarely four. The stalk or
common base on which they are set is not at all conspicuous, but when an attempt is
made to detach them they come off in twos or threes, and not separately. They are not
at all caducous. In most specimens they are oblong-ovate in shape; but in two (as in
Alder and Hancock’s figures) they are cylindrical. The tentacles and rhinophores are
both small, without a trace of perforations.
The jaws are thin, smooth, and colourless. The radula consists of a colourless,
continuous band, bent into a roughly semicircular shape, and bearing sixty to one
hundred denticulations like the teeth of a saw, and gradually increasing in size. Below
the row of denticulations (a) there can be seen under a high power three or four series
of minute pits and projections (b). No trace of any loose, detached teeth was found.
The oesophagus leads into a dilatation of moderate size, which may be called the stomach.
From it extends a diverticulum on either side which supplies two cerata. Posteriorly the
stomach is prolonged into a very wide sacculated gut, which extends to the extreme end
of the body and gives off simple diverticula, each of which supplies a single group of
cerata. These diverticula fill the cerata entirely, and no cnidocysts were found. The
contents of the digestive tract, including the cerata, resemble hardened jelly, and are
probably composed of the eggs of fish, which the animal is said to eat. In this jelly are
embedded moderately hard black lumps, detachable from their surroundings and easily
friable, which the jelly is not. . As mentioned, above, in some specimens this black
substance forms the major part of the contents of the digestive tract.
The lobes of the hermaphrodite gland are white, and visible through the dorsal
integuments. They are composed of small pouches containing ova, scattered rather
irregularly round a larger and more elongate pouch containing spermatozoa, and they
alternate with the diverticula proceeding from the alimentary canal to the cerata. There
is no armature on the penis. The renal organ consists of a simple sac with a few
constrictions. I t does not in my specimens extend so far backwards as is indicated by
Hecht’s figures (1, pi. iv, figs. 47, 48), but terminates soon after the commencement of
the posterior third of the body.
While the present work was going through the press, Mr. Evans, Lecturer in
Zoology at the University of Sheffield, made some careful and prolonged researches
into the anatomy and physiology of Galma glaucoides.1 He has most courteously
communicated to me the results, which he has tested by the examination of numerous
specimens. They are unexpected and of exceptional interest. He finds that G. glaucoides
has a very spacious stomach but no intestine and no anal opening, the excreta (which
owing to the nature of the food are relatively small in quantity) being retained within
the body in the form of the black matter mentioned above. In young specimens in
which the hermaphrodite loculi were immature, the sections showed recognizable
remnants of fish embryos. In older animals containing mature ova and partially emptied
male loculi, the contents of the stomach and of the hepatic diverticula in the cerata were
highly vacuolated and comprised inter alia black or brown excrement. In other
specimens the alimentary canal contained nothing but this dark excrement. Old
specimens twice the size of those mentioned were found to be gorged with albumen,
which was uniform and unvacuolated except for a black core of excrement running
through the whole length of the stomach. Mr. Evans thinks that the animals live two
years and that this stage represents the second year. To the best of my belief this
arrangement of the alimentary organs has no parallel among the Mollusca. It seems to
depend on the exceptional quality of the food, nearly the whole of which can be
assimilated.
Mr. Evans further notes that the cerebro-pleural ganglia are fused and of the same
size as the pedal ganglia, which lie at the sides of the oesophagus. There are no
visceral ganglia as in the Ascoglossa. The buccal and rhinophorial ganglia are large,
the latter sessile on the cerebro-pleural ganglia. The gastro-oesophageal ganglia consist
1 It is of course possible that Forestia mirabilis may not possess the same peculiarities as
, Galma glaucoides. If so, the two genera will still have to be kept distinct.