23 2 DISCOVERY REPORTS 



runs forward to end on a levator muscle of the labrum. In a similar position in Dolor ia 

 I described a small frontal ganglion, but this is not present in Gigantocypris. 



The posterior nerve running upwards from the labral ganglion is a thick nerve which 

 immediately penetrates underneath the circular muscles of the oesophagus. This forms 

 a branching system similar to, but of a different pattern from that which I described 

 for Doloria. In the latter form it originates from two outgrowths of the labral loop. 

 In Gigantocypris it commences as a single nerve which then divides immediately it has 

 penetrated the layer of circular muscles. The two branches so formed run up the sides 

 of the oesophagus and connect with the stomach ganglion. They give off various branches, 

 one of which from each side extends inwards to form a median nerve which ends before 

 reaching as far as the stomach ganglion. This oesophageal plexus is thus similar to that 

 of Doloria, but in Gigantocypris it was found possible to isolate it from its overlying 

 musculature and to study it as a permanent stained preparation. 



The stomach ganglion occupies the same position as in Doloria, that is, the bay 

 between the aortic oesophageal muscles (Figs, n, 12). It gives off a number of major 

 branches. Two of these have been mentioned, the labral connective and the branch 

 penetrating the circular muscles to bifurcate into the oesophageal plexus. Laterally it 

 gives off branches which connect up with a plexus of nerve cells supplying the dilator 

 muscles of the oesophagus. This plexus has not been inserted in any of the figures 

 because, while it does concentrate into two main tracts running down the sides of the 

 oesophagus but outside the circular muscles, it would be misleading to figure it in the 

 same way as the definite connectives which have already been described. It is really a 

 pair of chains of stellate nerve cells (Plate XLI, fig. 4) which are connected throughout 

 the length with all the various dilator muscles. Ventro-posteriorly the chain on either 

 side makes a very definite connexion with the nerve ring in the tritocerebral region, 

 that is, at the level of the mandibular outflow of nerves. 



From this anatomical description I think it can be deduced that among other functions 

 the stomach ganglion controls the peristaltic movement up the oesophagus. The anterior 

 outflow which lies underneath the circular muscles I take as the motor supply to these 

 muscles, that is, the constrictor system, although I have not been able to see any actual 

 nerve ending on them. The postero-lateral chain of nerve cells is the motor supply to 

 the dilator system. It is significant that this latter group of nerve cells connects with 

 the nerve ring in the mandibular region. I have not, however, been able to find any 

 internal connexion to the mandibular nucleus. 



Anteriorly the stomach ganglion gives off a median nerve which, after a short distance, 

 penetrates the floor of the aorta and enters the latter (Fig. 12). It extends up the aorta 

 to about the level of the aortic tendon, that is, at the base of the aortic and pericardial 

 dilator muscles. Here it bifurcates into two short branches (Fig. 16) which extend 

 laterally to two elongated aortic ganglia. The latter extend both up and down the aorta. 

 Upwards they stretch close against the aortic muscles to a point where this muscle meets 

 the nauplius eye muscle. At this point they send numerous attenuated connexions to 

 a similar ganglion extending some distance down the latter muscle (Fig. 10) and I am 



