OBSERVATIONS ON THE NERVOUS SYSTEM OF APUS. 441 
take up a position near those of the first thoracic feet. The 
two last pair of emigrated ganglia, reduced to a small size 
in consequence of the rudimentary condition of the corre- 
sponding appendages, have lost every sign of a commis- 
sure (fig. 2). 1 The ganglia of the anterior antennae show, in 
the brain, nervous fibres which unite them with one another. 
The facts we have observed in Apus, in regard to the anten- 
narv nerves, do not constitute an isolated case in contradiction 
with what is remarked among other animals of the same 
class. If one compares the nervous system of Apus with 
that of other Crustacea, a great concordance is found on 
the contrary. 
Let us take a type in every family of the Branchiopodous 
Phyllopods. In Limnetis 2 the first antennary nerve comes 
equally out of the cord, but immediately behind the brain. Its 
ganglion is evidently held in the brain, just as in Apus. The 
posterior antennae have a distinct pair of ganglia joined by a 
postoesophageal commissure. 
In Branchipus 3 the nerve of the anterior antenna arises 
at the posterior part of the brain out of a group of cells distinct 
from the primitive cephalic ganglia; the nerves of the posterior 
antennae, just as in Limnetis, come out a pair of cellular 
groups joined by a postcesophageal commissure. 
Among Cladocerous Phyllopods Daphnia 4 shows a condition 
very like that of Branchipus. 
In the Amphipod Phronima, 5 the nerves of the second pair 
of antennae are also observed coming out of the abdominal 
cord, a little behind the brain. 
1 The two first postoesophageal commissures belong to the elongated 
ganglia of the stomatogastric nerve. 
2 Grube, “ Bemerkungen fiber die Phyllopoden,” * Archiv ffir Naturg.,’ 
1853. 
3 Claus, “ Zur Kenntniss des Baues von Branchipus, &c.,” ‘ Abhandl. 
der K. Gesellsch. der Wissensch.,’ Gottingen, 1873. 
4 Claus, “ Zur Kenntniss der organisation der Daphniden,” c Zeitschr. ffir 
wiss. Zool.,’ t. xxvii. 
5 Claus, “Der Organismus der Phronimiden,” ‘Arbeiten aus dem Zool. 
Inst. Wien,’ t. ii. 
