THE BRAIN OF THE LOCUST. 
225 
hairs on the crust of the insect, or from the antennae, or the eyes or ears, 
and end in separate masses or lobes, which are modified ganglia, such 
ganglia are regarded as " sensory ganglia," and the nerves leading in 
from them are ealled ingoing or " afferent nerves," while the ganglia 
which give rise to the outgoing or " efferent" nerves, i. e., those going to 
the muscles of the wings, legs, &c, are called " motor ganglia," as 
stated by Bastiau, in bis popular and excellent work " Tbe Brain as an 
Organ of Mind." As to the term ganglion we quote as follows from 
Bastian: 
Two or more sensory ganglia, or two or more motor ganglia, may grow together into 
a single mass ; or, what is equally common, a sensory and its corresponding motor 
ganglion, or two or more pairs of these, may fuse into a single larger nodule, which 
may he called a " nerve-center." The term ganglia is, however, commonly applied 
to any round, ovoid nodule containing nerve-cells, whatever its size or degree of in- 
ternal complexity. Many ganglia in the lower animals, which are typically deserv- 
ing of the name as regards mere form and separateness, are also, hy reason of their 
compound nature, true nerve-centers. The two terms are, therefore, to a considerable 
extent, interchangeable. 
Beferring the reader to Bastian's book, or to the text-books on physi- 
ology by Huxley, Foster, or Dalton, for information regarding the 
structure and physiology of the nervous system in general, we will pro- 
ceed to describe that of the locust. It should be borne in mind, how- 
ever, that the subcesophageal ganglion, or " brain," of the insect is much 
more complex than any other ganglion, consisting more exclusively both 
of sensory as well as motor ganglia and their nerves. But it should 
also be borne in mind that the suboesophageal ganglion also receives 
nerves of special sense, situated possibly on the palpi and possibly on the 
tongue, at least the latter is the case with the bee ; hence, this ganglion is 
probably complex, consisting of sensory and motor ganglia. The third 
thoracic ganglion is also, without doubt, a complex one, as in the locusts 
the auditory nerves pass into it from the ears, which are situated at the 
base of the abdomen. But in the green grasshoppers, such as the katy- 
dids and their allies, whose ears are situated in their fore legs, the first 
thoracic ganglion is a complex one. In the cockroach and in the Leptis 
(Chrysopila), a common fly, the caudal appendages bear what are prob- 
ably olfactory organs, and as these parts are undoubtedly supplied from 
the last abdominal gangbon, this is probably composed of sensory and 
motor ganglia ; so that we have in the ganglionated cord of insects a 
series of brains, as it were, running from head to tail, and thus in a still 
stronger sense than in vertebrates the entire nervous system, and not 
the brain alone, is The organ of the mind, or psychological endowment, 
of the insect. 
We will now proceed to examine the brain of the adult Caloptenus 
spretus, and compare it with that of other insects; then study its devel- 
opment in the embryo, and finally examine the changes it undergoes in 
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