436 
PAUL PELSENEEE. 
first antennarv nerve proceeds from the primitive cephalic gan- 
glion ; if, on the contrary, the brain comprises the first anten- 
nary ganglion it is a svncerebrum. It -will be stated further 
on, under No. Ill, that the latter hypothesis is the true one. 
The second antennarv nerve, when coming out of the cord, 
goes immediately forward. In examining that part of the 
nervous system under a low power of the microscope, one 
observes the following disposition (fig. 2) : the fibres of the 
second antennary nerve go into the abdominal cord (c a) from 
in front backwards, towards the elongated swelling (ra), The 
latter is situated upon the internal side of the cord and pro- 
trudes rather strongly. In the interior of the cord, towards 
its external side, one observes another smaller group of nerve- 
cells (g a). It is a small ganglion, composed of a few cells, 
and there the fibres of the first antennary nerve end. 
From the preceding statements it results : 
1st. That the elongated ganglionic swelling does not repre- 
sent the fused ganglia of the first and of the second antenna. 
2nd. That the two pairs of antennary ganglia have not disap- 
peared ; they still remain in a very distinct manner. The 
second antennary nerve comes indeed from a small ganglion 
situated in the cord in an external position to the elongated 
swelling ; and we shall see further on that the fibres of the 
first antennary nerve come from a special and distinct ganglion, 
situated on the posterior part of the brain. 
As for the maxillipede nerve, its fibres go to a small ganglion 
which is found in the cord a little in front of the first thoracic 
foot ganglion. Therefore, as in the case of the two antennae, 
the ganglion has not disappeared. 
II. The ganglionic elongated swelling (r a) is joined to its 
homologue by a double commissure, like all the ganglia of 
the ventral cord. According to Zaddach (loc. cit., pi. iii, 
fig. 5, e), it seems that the anterior commissure comes out of 
the stomatogastric nerve. But, when dissected (fig. 2), both 
the stomatogastic nerve (n s) and the commissure (c i) are seen 
coming out of the elongated ganglion. 
The homologue of the latter exists also among Decapods. 
