REPOET ON THE PTEROPODA. 
73 
very widely separated from the pedal. To this I should reply that in the Dibranchiate 
Cephalopoda, as has already been said, we may observe, in the degree in which the 
brachial ganglia are separated from the pedal, a whole series of successive stages ( Ommcito - 
strephes, Sepiola, Loligo, Sepia, Octopus ), in which the brachial ganglia are gradually less 
and less distinctly separated, and in. the last-named form a single mass, and are only marked 
off by a slight constriction. 
I may further remark that this gradual separation of the brachial from the pedal 
ganglia, which is seen in passing from Octopus to Ommatostrephes, corresponds to an 
equivalent separation between the “ superior buccal ” and cerebral ganglia, the former 
separating from the latter even more than the brachial ganglia separate from the pedal. 
Whatever be the separation of the brachial and pedal ganglia, the pedo-brachial connec- 
tive always remains much more important than the cerebro-brachial. 
Thus then the great removal of the brachial and pedal ganglia (in Ommatostrephes ) 
is not a primitive arrangement. It is adventitious, and due to the cause which separates 
at the same time all the anterior portion of the main mass of the central nervous system, 
as well supracesophageal as subcesophageal. 
Primitively, the brachial and pedal ganglia of the same side must have been in close 
apposition, as is shown by the observation of the development of the Decapoda (alluded 
to above) and as appears still to be the case in Cirroteuthis, according to the figures of 
Reinhardt and Prosch . 1 
In Nautilus, which is the most primitive of all, this separation of the brachial from 
the pedal ganglion has not yet taken place ; in the female , 2 however, there is found a 
small ganglion corresponding to a part of the brachial ganglion, which innervates the 
internal labial appendages. But all the appendages of the male and the other append- 
ages of the female are innervated directly by the anterior suboesophageal ganglionic ring, 
and the nerves to the funnel are seen to issue at the side of the last ventral “tentacular” 
nerves. 
Some have desired to see in this anterior suboesophageal ring, which corresponds to 
the brachial and pedal ganglia of the Dibranchia, an external pedal portion and an 
internal cerebral portion. But in this case the latter would be only lateral and would 
not extend below the oesophagus (compare the figure of von Jhering 3 ). This part would 
then innervate the tentaculiferous appendages ; in this way it is sought to prove the 
cephalic nature of these latter. 
This division is, however, quite imaginary, and it has remained invisible to those 
zoologists who have not been prejudiced by attempting to prove the cephalic nature of 
the appendages (Owen, Valenciennes, &c.). In reality this ring is entirely pedal, and 
1 Om Sciadephorus Mullen, K. dansk. Vidensk. ISelsk. Afliandl., p. 19, pi. v. fig. 2. 
2 Owen, Memoir on the Pearly Nautilus, pi. vii. fig. 8. 
3 Vergleichende anatomie de Nervensystemes und Morphologie der Mollusken, p. 262, fig. 14. 
(ZOOL. CHALL. EXP. PART LXVI. — 1888.) Uuu 10 
