286 The Brain of the Locust. [ April, 
behind the mouth and under the cesophagus, hence it is called 
the subwsophageal ganglion, (Plate 1, Fig. 5.) The brain really 
is a double ganglion, being composed of two hemispheres, each 
hemisphere being a single ganglion or nerve-center ; all the suc- 
ceeding ganglia are also double ganglia; but for convenience 
we will call the “brain,” and each: of the succeeding nerve- 
centers a ganglion. Each side of the brain contracts, and then 
swells out into a rounded portion next to the eye, called the 
optic ganglion, (Pl. 1, Fig. 1.) From this optic ganglion the 
optic fibers proceed to the facets of the eye. The optic gan- 
glion connects with the Lrain by the large optic nerve. There 
are, then, two offic nerves, besides three slender nerves (ocel- 
lar nerves) sent to each of the three oce//i or simple eyes ; more- 
over, a nerve is sent to each of the antennz, and are hence called 
the antennal nerves. The relations of the brain to the head, and 
to the succeeding ganglion, and the origins of the nerves distrib- 
uted to the eyes, antennz and ocelli, as well as of the nerves 
sent to the jaws, etc., are clearly seen in the figures on Plate 1. 
On the other hand the mouth parts, z. ¢., the jaws (mandibles) 
and accessory jaws (first and second mcitibe. the latter called the 
fabium or under lip) are each supplied by a pair of nerves, called 
respectively the mandibular, maxillary and labial nerves. These 
three pairs of nerves arise from the subcesophageal = 
(See. Pi 1; Fig. 2: 2) 
The Brain of Insects as distinguished from the Brain of Verte- 
brates —The “ brain,” or supracesophageal ganglion is, as we shall 
see, a much more complicated organ than any of the succeeding 
ganglia, having important parts which are wanting in all the 
others, hence it is par excellence nearer to our idea of a brain than 
any of the other nervous centers. It should be remembered, 
however, that the word, “brain” is applied to this compound 
ganglion simply by courtesy and as a matter of convenience, as 
it does not correspond to the brain of a vertebrate animal, the 
brain of the horse or man being composed of several distinct 
pairs of ganglia. Moreover, the brain and nervous cord of the 
fish or man are fundamentally different, or not homologous with 
those of the lower or invertebrate animals, though the nervous 
system of the insects and Crustacea present greater analogies to 
that of the vertebrates than any other of the lower animals, with 
the exception, perhaps, of the cuttlefish. The nervous cord of 
