374 PROFESSOR E, RAY LANKESTER, 
intimate structure of the cerebral ganglion of Arthropods 
(e.g. of Astacus, of Blatta, and of Limulus). It appears to 
me that it wili be of very great importance in this analysis 
to determine first of all the characteristic structure of the 
archi-cerebrum of Chztopoda, of Apus, and of Limulus, 
and then to advance to the composite syn-cerebra of the 
higher Crustacea, when it may be possible to distinguish as 
distinct morphological elements the nucleus furnished by 
the archi-cerebrum and the later accretions of primarily 
postoral ganglia. Possibly such a method of analysis may 
help in deciding whether the Hexapods’ and Myriapods’ 
antenna is a true outgrowth of the prestomial region (like 
the tactile processes of Chetopods) or a postoral appendage 
which has moved forwards. 
Returning again to the woodcut diagram of the anterior 
portion of the nerve-cords of Apus (fig. 2), it will be 
observed that there are some other remarkable features 
besides the pure archi-cerebrum and the widely separated 
position of the lateral nerve-cords. 
The nerves to the first and to the second antenne come 
off from the lateral cord just in front of the elongated gan- 
glionic swelling (G1), which is joined to its fellow of the oppo- 
site side by two transverse commissures, as are the more 
posterior ganglia. A secondary cesophageal ring surrounding 
the dotted area of the cesophagus (2) is given off from the’ 
anterior of these transverse commissures, which are both 
post-cesophageal, and accordingly determine the ganglia (G 1) 
as post-cesophageal. 
The question arises whether these elongated ganglia re- 
present the fused ganglia of the antenna and antenne. 
Possibly they do; in any case it is an altogether remarkable 
fact that there exists in Apus a pair of ganglia behind the 
cesophagus in front of the pair which are appropriate to the 
mandibles. 
There is no such arrangement known in any other Crus- 
tacean excepting in Limnetis, where, according to Grube, 
there are actually ¢wo distinct pairs of ganglia in this posi- 
tion, the interior of which supplies the second pair of antennze 
with nerves, whilst the first pair of antennz are supplied 
from the lateral cords at the base of the cerebrum. On 
account of the small size of Limnetis some doubt may be 
entertained as to the complete accuracy of Grube’s observa- 
tions, but they tend very strongly to establish the general 
accuracy of those of Zaddach upon Apus'. 
1 IT have not been able in my specimens of Apus, on account of their 
state of preservation, to make dissections of the uervous system ; I should 
