97 
thereby indicating their original duplicity. The cephalic ganglion is considerably 
larger than the others, and of a rounded quadrangular form. It occurs, as stated 
above, quite in front dorsally, below the anterior part of the frontal lobe of the 
carapace (see PI. LXV—LXVIII, fig. 1 , C. gl). Its dorsal face (see PI. LXYI, 
fig. 3) is rather uneven, being divided into several lobes by more or less deep 
grooves, one of which, running along the middle, is especially distinct and 
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 antennae 
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 
system. 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 maxillse. 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 
ganglia, 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. 
