The anatomy of a pteropod, Corolla (Cymbuliopsis) spectabilis Dall. 73 



sheathing the oesophagus. It is impossible to state positively the extent 

 of this system but several times it has been found to extend as far 

 forward as the level of the tentacles and posteriorly as far as the 

 anterior fifth of the stomach. Whether it extends over the wall of 

 the mouth cavity and over the stomach and possibly the intestine is 

 not at present known. Some of the finer nerves of this anastomosing 

 system connect here and there with ganghon cells. In sections also 

 these are readily seen owing to their relatively large size, darkly 

 staining chromatin and to the fact that they are slightly elevated 

 above the general surface of the oesophageal wall. While they ap- 

 pear in surface view to be bipolar, sections often appear to show one, 

 rarely two, additional fibres passing inward. It is possible that the 

 cerebral nerves {c^,c^) supplying the anterior portions of the digestive 

 tract take no part in the formation of this plexus but especially 

 favorable preparations appear to show some of their finer branches 

 uniting with it. 



The pedal ganglia (Figs. 4, 5 p), located in front of and below 

 the cerebral ganglia are united by two commissures of which the 

 more anterior (d) is relatively long and delicate. Each ganglion gives 

 rise to three main nerves. The first (Figs. 3—5 2^^) arises anteriorly 

 and. extending outward and forward becomes distributed to the 

 margin of the proboscis. Anastomoses between the distal branches 

 are not infrequent and a few preparations give indications of an 

 extensive network. A short distance beyond the point of origin 

 of this nerve a delicate fibre arises and bending backward unites with 

 the larger of the lateral pedal nerves. From it a branch extends 

 forward whose fibres appear to be distributed entirely to the walls of 

 the oesophagus. This connecting nerve with its branch is a perfectly 

 constant feature and is invariably present on both sides. The smaller 

 of the lateral pedal nerves (p^) passes outward and forward into the 

 tissue of the fin where it breaks up into an extensive system of 

 branches increasing in number as the margin is approached. At this 

 point they enter innumerable pigmented groups of cells and are un- 

 doubtedly sensory. On the other hand since the lateral pedal nerves 

 are the only ones supplying the foot it is evident some of their fibres 

 are motor in function. In many cases where the branches of these 

 nerves cross some of the muscle bands of the fin their surface pre- 

 sents a roughened appearance that under high magnification appears 

 to be due to delicate nerve fibres entering the muscle. In the same 



