REPORT ON SPIRULA. 
15 
Their axis rises between the nidamental glands, properly so-called, and the accessory 
glands. These organs are retained at the internal face of the mantle at the dorsal side 
of their axis, by a support (“ pallio-branchial ligament,” PI. I. fig. 6, pb.), upon which 
no “ spleen ” or blood-gland is to be observed. In front of the branchial support, and 
more ventrally, the internal face of the mantle shows a lateral cartilaginous prominence 
(“ button ” of the resistance apparatus) ; an elongated prominence of the same appear¬ 
ance exists (at least in Spirula reticulata') on the dorsal side of the internal face of the 
mantle, on the median line, anteriorly, opposite to the middle of the infundibular collar. 
II. Nervous System. 
As in all Cephalopods (including Nautilus) the central nervous system is situated 
around the oesophagus behind the buccal bulb (PI. IIP), and, as in the Dibranchiates, 
this nervous system is contained in a cartilaginous capsule (PI. V. figs. 1, 3), which was 
treated of above. 1 
Setting aside the enormous optic ganglia (PI. V. fig. 2, o.g.), which occupy the 
right and left sides of the central nervous mass, we recognise in this last the following 
ganglia :—(A) One pair of supra-oesophageal: cerebral ganglia (PI. V. figs. 1,2, 3, g.c.), and 
(B) three pairs infra-oesophageal: ( a ) anterior : brachial ganglia ( g.p' .); (b) median: pedal 
ganglia ( g.p .) ; ( c ) posterior ; pleuro-visceral or “ chlamydo-splanchnic ” ganglia ( g.ch.s .). 
Besides, it is necessary to distinguish still another little pair, anterior supra-cesopha- 
geal, called “superior buccal” ( s.b.g .), far removed 
from the cerebral centres, as in the (Egopsids (Fig. 
L, ix), although in the Sepiidse they are very much 
nearer, and in the Octopods they are fused with 
them, forming the anterior part. 2 
These “ superior buccal ” ganglia are united 
to the cerebral ganglia by long connective cords ; 
in the Challenger specimen the left connective cord 
shows the peculiarity of being double (PI. V. fig. 2). 
The connective cords uniting the superior buccal 
ganglia to the brachial centres have not been seen 
and have probably escaped notice; but the cerebro- 
brachial cords have been observed and are rather long (PI. Y. fig. 4, x). 
1 Ventrally and laterally the central nervous system is surrounded and separated from the cartilage by 
a glandular looking substance (PI. III., ad., and PI. V. fig. 1), as in other Dibranchiates (where it is called 
“ white body ”), the microscopic examination of which suggests that it is a blood gland. 
2 The facts that this segmentation of cerebral centres exists in a form so archaic as Spirula, and that the 
superior buccal ganglia resulting therefrom are very far removed from the cerebral ganglia properly so-called, 
prove that the disposition presented by the Octopods is not the primitive one. 
Fig. L.—Central nervous system of Ommatostreph.es 
pteropus, left hand side view; magnified, i, 
buccal mass ; ii, brachial ganglion ; iii, pedal 
ganglion; iv, pleuro-visceral ganglion; v, posterior 
salivary glands ; v', oesophagus ; vi, section of 
the optical nerve ; vii, cerebral ganglion ; viii, 
stomato-gastric ganglion ; ix, “ superior buccal ” 
ganglion ; x, anterior salivary gland, uncovered. 
