_ 97 



tlierebv indicating their original duplicity. The cephalic ^an.elioii is considerably 

 larger than the others, and of a rounded quadrangular form. It occurs, as stated 

 above, i|uiU' in front dorsally. below the anterior pail of the frontal lobe of the 

 carapace (see PI. IAV -LXYII1. lig. 1. C. gl). Its dorsal face (see PI. LXVI, 

 I'm'. :!) i- rather uneven, being divided into several lobes by more or less deep 

 grooves, one of \vhieh. running along the middle, is especially distinct ;ind 

 divides the ganglion into ~2 symmetrical halves. Of the lobes, the ~2 median 

 ones, separated by the above-mentioned longitudinal groove, are narnow linear 

 in form, and in front curve abruptly outwards. 'i he nerves for the antenna' 

 seem to originate from the lower face of the ganglion, and this is probably also 

 the case with the optic nerves; but I have not been able to trace these nerves 

 distinctly. Behind, the comparatively short oesophageal commissures are sent off 

 (see fig. 2), connecting the cephalic ganglion with the ventral ganglionic chain. 

 From each of these commissures, a very large nerve-stem issues, ascending to 

 each side immediately behind the cephalic ganglion, and curving backwards 

 along the dorsal side (see also PI. XXXVI, middle fig.). It sends off numerous 

 nerves to the strong mandibular muscles, and apparently also provides the stomach 

 and the heart with nerves, thus representing the visceral part of the nervous 

 M'stem. Of the ganglia belonging to the ventral chain, the 3 anterior ones are 

 placed close together, and the commissures connecting the 2 foremost ones are 

 almost obsolete, though a small opening is seen between them in the middle. 

 The 3rd ganglion is considerably larger than the 2 anterior ones, and also 

 somewhat exceeds the next succeeding ones in size. It belongs to the segment 

 carrying the 1st pair of maxillipeds with their voluminous branchial appa- 

 ratus, the 2 preceding ganglia being destined for the 2 pairs of maxilla?. The 

 7 remaining ganglia belonging to the anterior division of the body are of 

 rather uniform appearance, and are connected by well-defined slender commis- 

 sures, between which, moreover, a median longitudinal nerve-stem is seen (see 

 fig. 4). They each send off laterally several nerves, and from the anterior part 

 of the commissures, issues another slender nerve extending upwards and outwards. 

 The hindmost of these ganglia is somewhat smaller than the others, and the 

 commissures connecting it with the preceding ones are rather short. The caudal 

 uanglia, as above stated, are very small, and only indicated by a slight thickening 

 of the commissures, which at this place assume a cellular structure, and are 

 confluent in the middle (see fig. 5). The last caudal ganglion, however, (see 

 fig. 2) is more distinctly defined, and sends off nerves behind to the telson and 

 the uropoda. 



