THE ORGAN OF VERRILL IN LOLIOO.
97
The Organ of Verrill in Loligo.
By
Malcolm Laurie, B.Sc.
From the Zoological Laboratory of University College, London.
With Plate XI.
IN a paper on North American Cephalopoda1 Verrill describes
a valve-like organ at the base of the siphon in Desmoteuthis
and Taonia, in both of which genera the true valve is absent.
His drawing of this structure in D e s m o t e u t h i s t e n e r a is reproduced infig.1. I t is there seen to be composed of a median
portion, (m.) lying on the dorsal side of the siphon, and a pair
of lateral cushions (re. ri.). The median portion is raised into
three papillae, one (i.) median and a pair (i'.) more posterior in
position.
This structure to which the name of Verrill's organ has
been given by Hoyle2 has been observed in a few other species,
but is by no means common. I t is figured by Mr. Weiss in
the present number of this Journal for several Oigopsidse (see
PI. VIII,fig.3 ; PI. IX,fig.8 ; PI. X,fig.10). I was therefore much interested to discover, in sections of a young
Loligo about 6 mm. in length, made in Professor Lankester's
laboratory at University College, London, a structure in the
siphon which I think there is no doubt is Verrill's organ.
The general appearance of this structure is shown infig.2.
It consists of a median dorsal cushion, which is prolonged
1
3
' Trans. Conn. Acad.,' vol. v, part 2.
' Challenger Report,' vol. xvi.
VOL. XXIX, FART 1 .
NEW SER.
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98
MALCOLM LAURIE.
backwards into two large processes, and a pair of lateral
cushions on the ventral wall of the siphon. The dorsal
cushion is produced forwards into a papilla which is best seen
in section (fig. 6, i.). Figs. 3—6 show sections through the
siphon and VerrilFs organ. The valve (figs. 2 and 6, v.) is
well developed, and quite distinct from Verrill's organ.
An examination of the histological structure shows the
organ to be glandular. It is composed (fig. 7) of columnar
goblet cells almost entirely filled with a clear transparent
substance which stains very darkly with hsematoxylin. The
nuclei are at the bottom of the cells, and are surrounded by a
small quantity of granular protoplasm. On the surface of the
organ, more especially in the older specimens, there is a large
quantity of mucus-like substance which has apparently been
excreted from the cells. The organ of Verrill thus appears to
be a mucus gland. It may, as Verrill suggests, function as a
valve in those forms in which a true valve is wanting, but such
a function would be secondary.
It is well developed in Ommastrephes in specimens about
8 mm. long. I can find no trace of it in the adults of either
Loligo or Ommastrephes.
As regards its use to the organism or its homologies outside
the Cephalopoda, I can say nothing. I think that Verrill has
no foundation for his suggestion1 that the dorsal cushion is " a
true homologue of the foot of Gasteropods." Its presence, so
largely developed in the young, seems to indicate that it is an
archaic structure in the group of Cephalopoda, but there are
no grounds for identifying it with any particular structure
existing in Gastropods.
1
Loc. cit., footnote p. 432.
THE ORGAN OF VERRILL IN LOLIGO.
99
EXPLANATION OF PLATE XI,
Illustrating Mr. Malcolm Laurie's Paper on the " Organ of
Verrill in Loligo."
List of Reference Letters.
s. SipUou. m. Mediodorsal cushion of Verrill's organ, n. »'. Lateral
cushions, i. Central papilla, i'. Lateral papilla?, p. Mantle, v. c. s. Superior
vena cava. v. Valve.
FIG. 1.—Siphon of Desmoteuthis tenera. Natural size. After Verrill.
FIG. 2.—Organ of Verrill in young Loligo. Dorsal cushion.
FIG. 2 a.—Ventral wall of Siphon, showing paired cushions.
FIG. 3.—Transverse section of young Loligo. x -6^-.
Fi&. 4.—Transverse section of young Loligo further down than Fig. 3.
FIG. 5.—Longitudinal sagittal section of young Loligo to one side of the
middle line. X -6^-.
FIG. 6.—Longitudinal sagittal section of young Loligo in middle line.
FIG. 7.—Section of part of the organ of Verrill in a young Loligo. x £-£Q.
n. Nuclei, mu. Mucus in the goblet cells, ma'. Mucus on surface of organ.
F.Kutt,Uh*Eainr