38 PSYCHE. 
large number of fibres. 
is intimately connected with the convolu- 
tions. Intercrossing of fibres occurs in 
each optic lobe, coordinating the vision of 
the components of each eye, but there is no 
intercrossing between those of opposite eyes. 
Dr. J. H. L. Flégel * makes the most 
important contribution yet given to the 
knowledge of the internal structure of the 
insect brain. 
sections of the brains of very many spe- 
cies, and the paper is accompanied by a 
dozen selected photographs from these 
preparations. In the cockroach, for exam- 
ple, he succeeds in making 60-80 trans- 
verse, and in one case even 350 longitu- 
dinal, sections. This insect was unexpect- 
edly found to have a remarkable brain de- 
velopment, perfectly comparable with that 
of the higher hymenoptera. The most im- 
portant parts of the brain are those form- 
ing a sort of interior framework, on which 
the rest of the brain is seemingly laid. Dr. 
Flégel proposes permanent names for the 
different parts of this framework, and finds 
that, starting with Blatta, the parts can be 
traced upwards through the brain of the 
hymenoptera, and downwards through the 
other orders. 
Some few of the facts given may be here 
mentioned. The wasps have a brain, at 
one end of the series. further removed from 
that of the ants and bees, than is the latter 
from Blatta. The saw flies stand lowest 
of the hymenoptera in the scale, while the 
ichneumons approach the ants. In the lep- 
idoptera, coleoptera, and indeed the other 
groups in general, the brain is simpler, al- 
though it can be easily homologized with 
the Blatta type. In caterpillars some parts 
He has made consecutive 
48 Zeitschr. wiss. Zool., v. 30, Suppl., p. 556. 
The front group: 
are-absent or very small, and easily over- 
looked, and the optical lobes of the imago 
are, moreover, drawn into the interior of the 
larval brain. Flégel emphasizes three 
points: the constant occurence of that part 
of the framework which he calls the ** cen- 
tral body,” in the adult, while it is almost 
obsolete in the lepidopterous larva, but not 
in the hymenopterous ; the size of the lobus 
olfactorius in insects with small antennae, 
but with evidently great olfactory powers, 
proves, Flogel believes, that the antennae 
are the seat of this sense. That they are 
not auditory organs appears from the fact 
that where these are elsewhere recogniza- 
ble, as in the orthoptera, they are not con- 
nected with any marked brain centre, like 
the olfactory lobes. Thirdly, although the 
so-called framework forms the principal 
part of the brain, there is absolutely no 
connection of its fibres with the other parts 
of the brain to be found, —a quite inex- 
plicable fact. A table illustrating the rela- 
tions between the brains of different insects 
is appended to the paper. 
Another very valuable contribution to 
this same subject is Mr. E. T. Newton’s 
paper * on the brain of the cockroach ; his 
results, reached without previous knowl- 
edge of Dr. Flégel’s paper, agree substan- 
tially with those of this author. For still 
further permanence of cerebral nomencla- 
ture, Mr. Newton latinizes Flogel’s names, 
and in one or two cases proposes different 
ones, for various reasons. The clearest 
figures yet given illustrate the external as- 
pect of the brain en face and in profile, 
while the figures of a model of the internal 
structures are very useful as a help to in- 
terpret the sectional views. A detailed de- 
49 Quart. Journ. Micr. Sci., v. 19, p. 340. 
zu 
