472 DISCOVERY REPORTS 



a single nerve to about half-way between the stomach ganglion and the labral loop. 

 Here it radiates into five nerves (Fig. lo A), of which two continue downwards and join 

 the labral loop laterally, the remainder disappearing in the gut musculature. These two 

 branches are joined together by a connective about the middle of their length. Their 

 junction with the labral loop is marked by a small swelling, which may represent the 

 visceral ganglion described by Hanstrom (1924, p. 33). 



The sympathetic system shows many points of resemblance to that of Astaciis as 

 described by Keim (191 5). The labral ganglion corresponds to the oesophageal ganglion 

 of Astacus. In the latter it is connected to the circum-oesophageal commissures by two 

 roots. In all my specimens of Doloria there is one large root on either side, but in one 

 specimen there are indications of a double root, and in all there are minute nerves, 

 apparently single nerve fibres, given off to the oesophageal musculature between the 

 two ends of the labral loop. 



The stomach ganglion is equivalent to the ganglion ventriculi superius. From both 

 a nerve originates which runs along the aorta. 



The connection between the stomach ganglion and the labral loop which lies inside 

 the oesophageal musculature corresponds to the nervus stomatogastricus inferior of 

 Keim. 



The connection which passes through the frontal foramen appears to correspond to 

 the two nerves, the nervus ventriculi impar inferior and superior, the former of which 

 runs from the oesophageal ganglion to the brain, the latter running from the brain 

 to the nervus stomatogastricus inferior and so to the stomach ganglion. However, these 

 are two separate nerves, both originating from the brain. In all my preparations of 

 Doloria which showed the sympathetic system clearly, this connection forms a distinct 

 loop passing through the frontal foramen, and does not show any connection with the 

 brain. However, it passes so close against the surface, that it is possible that a small 

 connection in this region exists. 



I could find no trace of a sympathetic system such as Liiders described in Giganto- 



cvpris (1909, p. 137). 



INTERNAL STRUCTURE 



The main nerve fibre tracts are shown in Fig. 9. I have made no attempt to study 

 this internal structure in detail, and have figured only those tracts which are conspicuous 

 and which appear to me significant. The fixation of the nervous system is so extra- 

 ordinarily good that, without doubt, a competent neurologist would be able to make out 

 many more connections than shown in the figure. 



The distribution of nerve cells is shown by the stippling in Fig. 9. The whole ventral 

 surface is a sheet of neurones, and these extend up the sides to the extent shown in 

 the figure. In addition, the dorsal surface of the fore-part of the brain and a dorso- 

 medial area at the hind part of the nerve ring are both covered with nerve cells. 



Among the neurones there are a number of giant cells but, apart from these, all are 

 of approximately the same size. Thus, as Hanstrom points out for Branchiopoda 

 (1928, p. 458), it is impossible to distinguish globuli cells. 



