142 Transactions. 



suckers, though the arm proper is normal in this respect. The entire arm 

 bears a succession of small photogenic organs scattered at various intervals 

 along its outer margin, and similar in general appearance (though many of 

 them are larger) to those near the tips of the first and second arms. On the 

 filament these appear as swellings or tubercles often half again as large in 

 diameter as the filament-stalk itself (fig. 3), but on the basal portion of the 

 arm they become rather deeply embedded, and are not easily seen except by 

 transmitted light. The basal portion, or arm proper, bears a heavy keel along 

 its entire outer aspect, and traceable almost as far as the margin of the eye- 

 iid. Including those borne on its terminal filament, the better-preserved arm 

 of this pair carries a total of 31 photophores, of which 4 are in the keel. 

 The ventral arms bear the usual fleshy fold along their outer margins, which 

 is broadened at the base to form a sheath for the tentacle ; they do not 

 appear to possess photophores. Suckers minute, in 2 regularly alter- 

 nating series on all the arms ; 16 to 18 pairs are to be counted on the right 

 third arm of one specimen, and 21 pairs on the right ventral arm. The 

 sucker-bearing face of each arm has a delicate trabeculated membrane 

 along either margin. 



Tentacles stout ; thick and fleshy at the base, thence tapering gradually 

 to the club ; laterally compressed ; inner surface flattened. A very slight 

 swelling is sometimes visible in the stalk a few millimetres from the base, 

 which, when mounted in xylol or balsam so that it can be examined by 

 transmitted light, is seen to mark the position of a small internal organ 

 which is undoubtedly photogenic. A somewhat larger swelling, rendered 

 more conspicuous by a thick aggregation of chromatophores on its outer 

 margin, occurs a few millimetres proximad from the club. When cleared 

 and mounted in balsam this is seen to mark the position of a much larger 

 double photophore, embedded in the tissues just beneath the patch of 

 chromatophores. In optical section (fig. 4) the organ shows an outer radially 

 .striate body (lenticular in longitudinal section) closely appressed within 

 the concave surface of a much larger body, shaped like a shallow oval saucer 

 (bean-shaped in longitudinal section). Both structures lie between the 

 muscular layers of the tentacle-stalk and the central nerve-cord, each of 

 which suffers a corresponding crowding and distortion. Tentacle-club 

 little or not at all expanded ; it is provided with a marginal web and armed 

 with 4 rows of small suckers with toothed horny rings. I have been unable 

 to make out the fixing-apparatus with sufficient clearness for description. 



In addition to the numerous photogenic organs already noted, there 

 are 8 others which are intrapallial, and therefore only visible in preserved 

 specimens upon opening the mantle-chamber. The most anterior of these 

 are the anal, a pair of small round greyish organs situated one on either 

 side of the rectum just below the base of the funnel. A little to the rear 

 of the middle of the visceral mass is a conspicuous half-circlet of 5 organs, 

 the median one pale in colour, oval in outline, flattened, and unpaired ; 

 the two neighbouring organs in close juxtaposition to the central one, very 

 large, likewise flattened and pale in colour. The terminal organs of the 

 .series are somewhat distant from the other three, one at the base of each 

 gill, and have the appearance of small flattened tubercles set in pigmented 

 cups. In the median plane of the body, considerably behind the centre of 

 bhe fins, is a single large flat lozenge-shaped organ of a pale colour, in con- 

 tact with which the tissues of the mantle are modified to form a conspicuous 

 lens-shaped thickening similar to that described by Chun for Thaumato- 

 lam/pas. 



