292 THE ENTOMOLOGIST. 
known as the hemispheres is proportional to the degree of 
development of intelligence and of manners, but that of the entire 
brain is not so. 
5. The nerves of the labrum do not, as commonly admitted, 
issue from the lower surface of the super-cesophagian ganglion. 
6. The study of insects having two thoracic ganglia shows 
that in some the first ganglion is simple, and corresponds to the 
first ganglion of the larva. The second is compound, resulting 
from the fusion of two or three thoracic ganglia of the larva with 
one or two of the abdominal ganglia. This is the case with the 
Lepidoptera, Coleoptera, Hymenoptera, and Neuroptera. In 
others both the first aud the second thoracic ganglia are com- 
pound, the former resulting from the fusion of the first and 
second thoracic ganglia of the larva. (Hmpis, Thereva, Asilus, 
Bombylius). 
7. The number of ganglia varies not merely in different 
species of insects, but even in different individuals of the same 
species. The working bee has five abdominal ganglia, whilst the 
males and the queen have only four; the working wasp has five 
ganglia, whilst the males and the queens have six. 
8. Hitherto it has been supposed that the last abdominal 
ganglion is always complex. I have often found that the last but 
one is formed by the union of several, while the last is simple. 
(In the working bee, in Mutilla, &c.) 
9. In certain insects (Tenthredo, Bombus), there exists in the 
thorax a sympathetic nervous system whose constitution corre- 
sponds to that of the abdomen in these insects. 
10. The transformation of the nervous system takes place 
according to two different types ; sometimes it contracts, and the 
number of ganglia is reduced in the adult (Hymenoptera, 
Coleoptera, Lepidoptera); sometimes the change follows the 
inverse direction, that is to say, in the larva there is only one 
single mass in the centre of the thorax (in addition to the sub- 
cesophagian ganglion), and this mass is broken up into a variable 
number of others, as M. Kiinckel has shown in Volucella, and as 
I have demonstrated in a great number of species (Hristalis, 
Volucella, Stratiomys, &e.) 
11. Comparative researches made on the nervous system of 
the Hemiptera show that when these insects have only a single 
thoracic ganglion it corresponds to the two hinder thoracic 
