440 
PAUL PELSENEEK. 
ment which has here a greater thickness. That mass seems to 
he common to the brains of all Crustacea, both inferior (Bran- 
chi pus) and superior (Astacus), and is also to be found on 
the anterior and posterior edges of the abdominal ganglia 
(fig. 9, a a and a p). 
IV. The second antennary ganglion is situated next the first 
postoesophageal commissure (fig. 2). Its position determines 
in consequence this appendage as equally postoesophageal. 
There cannot remain any doubt about the second antenna ; 
it is a metastomial appendage. 
Is it the same with the first antenna ? 
Yes it is. The point where its nerve comes out of the 
abdominal cord evidently shows that the ganglion correspond- 
ing to that appendage must originally have been found far behind 
the prostomial cephalic ganglia (properly called cerebral 
ganglia). If it were not so the nerve, instead of coming out of 
the cord, would come out of the posterior part of the brain, 
as among other Phvllopods, Branchipus, e. g. Besides, we 
have seen that the ganglia from which come the anterior anten- 
narv nerves have the structure of the abdominal ganglia, and 
therefore that they are ganglia of the abdominal cord. They 
were then originally postoesophageal, as well as the ganglia of 
the posterior antennae. The corresponding appendages are 
thus also metastomial appendages. 
We observe, then, that in Apus, in the anterior (praegenital) 
part, every pair of appendages, the two pairs of antennae, and 
the maxillipedes included, is provided with a pair of ganglia. 
Morover, the two pairs of antennae are metastomial, as well as 
the following appendages. 
We observe, too, that every ganglion has a kind of attraction, 
not only upon its homologue of the other cord, but even upon 
the preceding and following ganglia situated on the same cord. 
We see thus that the ganglia of the anterior antennae run all 
along the cord to come into juxtaposition with the primitive 
cephalic ganglia ; we observe also that the ganglia of the pos- 
terior antennae pass to a place near the elongated ganglia of 
the stomato-gastric nerve, and that the maxillipede’s ganglia 
