NERVOUS SYSTEM 471 



position. This possibility is supported by the constitution of the maxillary basal ganglia, 

 which are still partly a diffuse network of nerve cells lying close underneath the ecto- 

 derm. In this case they would not be physiologically comparable with the parapodial 

 ganglia of Polychaetes in which ganglion cells occur (Hamaker, 1898). 



If, however, they are simply accumulations of sensory cells, these cells cannot be 

 the usual type of bipolar cells which are always figured in the Crustacean antennulary 

 ganglion. For, in the latter ganglion of Doloria, as I have described, the bundle 

 of fibres constituting the antennulary nerve bifurcates on entering the basal ganglion. 

 One branch extends through the ganglion and the other curves round to the median 

 posterior angle, and from this corner another set of fibres extends distally through 

 the ganglion. Now these two sets of fibres must either belong to diff^erent groups 

 of nerve cells, in which case it is probable that true ganglion cells are present in 

 the basal ganglion, or else they must be the centrifugal and centripetal branches of 

 unipolar cells situated in the corner of the ganglion. That is, they are axons of cells of 

 the type usually described as characteristic of the vertebrate spinal ganglion (Parker, 



1919, p. 211). 



SYMPATHETIC SYSTEM 



Hanstrom (1924, p. 33) has recently described in Cypris fuscata a labral ganglion 

 (Lippenganglion), which is joined by a loop to the lower side of the posterior part of 

 the circum-oesophageal commissure, the junction being marked by a swelling which 

 he terms the visceral ganglion. Turner (1896, p. 30) describes a similar state of aflFairs. 

 He mistakenly refers to the "labial nerve or nerve to the upper lip ", but it is impossible 

 from his figures to determine exactly what he was attempting to describe. 



Liiders (1909, p. 137) describes a few minute median ganglia connected with the 

 ventral chain in Gigaiitocypris which he terms sympathetic ganglia. 



The sympathetic system of Doloria (Figs. 10 A, B) is well developed and agrees with 

 that of other Crustacea. The mandibular swellings are connected by a loop, which 

 originates just in front of the mandibular nerves and passes close against the front 

 wall of the oesophagus, and which may be termed the labral loop. This is enlarged 

 medianly into a ganglion, the labral ganglion, which extends a considerable distance 

 dorsally just outside the circular muscles of the oesophagus. It continues upwards as 

 a thin nerve to the frontal foramen of the brain (Fig. 10 A). Here it meets another nerve 

 which extends from a small ganglion — the frontal ganglion — consisting of two or three 

 cells, situated at the base of the frontal apodeme. The two nerves pass through the 

 foramen, uniting in doing so, and are then joined by another nerve which can be traced 

 to the aortic roof and the pericardial dilator. The fused nerves run backwards to a 

 globular ganglion — the stomach ganglion — situated at the junction of oesophagus and 

 stomach. This lies embedded in gut parenchyma between the aortic oesophageal 

 muscles, and gives off" branches to them. Posteriorly it gives off a small nerve towards 

 the stomach. Antero-ventrally it gives off a nerve which, almost at once, penetrates 

 underneath the circular musculature of the oesophagus. I have succeeded in tracing 

 this nerve without any doubt in both sagittal and frontal sections. It passes down as 



