398 Miscellaneous. 



demonstrated that coordination of all the movements of the appen- 

 dages takes place regularly in decapitated insects. The subceso- 

 phageal ganglion principally governs the appendages of the mouth, 

 and differs but little in its histological structure from the other 

 nodes of the ganglionic chain. As to the cerebroid or supraceso- 

 phageal ganglia, they are the seat of nearly all the functions of the 

 hemispheres of the brain in vertebrates. There are situated the 

 organs of the perceptions, of memory, of intelligence, <fcc. Hence 

 they have a more complicated histological structure. These ner- 

 vous centres are nevertheless constructed on the same general plan 

 as the other ganglia. In the middle they present bundles of ner- 

 vous fibres, while the nerve-cells principally occupy the periphery. 

 Towards the centre of the ganglion there are three groups of small 

 cells arranged in stages one above the other and communicating by 

 numerous fibres. The group situated in front of the others may be 

 regarded as having the most intimate relations with the convolu- 

 tions (or organs in the form of a horseshoe), which are especially 

 developed in the social Hymenoptera, the most intelligent of insects. 

 The greater or less development of these parts of the nervous 

 system coincides with the intellectual development. Thus we find 

 the most remarkable development in the working ants, and then in 

 the working bees ; there is a less development in the female ants 

 and in the queen bee. In the males these parts only exist in a 

 rudimentary state. Sexual life, and especially the development of 

 the ova and semen, are therefore opposed to the development of 

 these organs. AVe can easily trace the bundles of nervous fibres 

 which run from the base of the ganglion to the convolutions. 

 From the sides of the ganglia issue the lobes which go to the com- 

 pound eyes. In the humble-bees, in which each eye occupies 

 nearly half the head, these lobes have an enormous development. 

 They are of an oval form, and composed, in the median part, of 

 short cylinders arranged in series. 



These cylinders give origin to the fibres which penetrate into the 

 base of the brain. In the exterior part of the optic lobes these 

 fibres interlace and present the form of two flattened cones with their 

 apices turned towards each other. In this way the fibres of the 

 left side appear upon the right side, and the inferior fibres become 

 superior. Each fibre by thus changing its direction enters into the 

 constitution of the optic nerve which runs to each of the eyes 

 forming together the compound eye. The intercrossing of the 

 fibres does not occur here bet veen the two opposite eyes as in the 

 chiasma of the vertebrates, but between the eyes of the same side 

 of the head. Such an organization very probably causes a perfect 

 coincidence between all the optical impressions received separately 

 by each eye. 



To obtain the preparations which have given me these results, I 

 extracted the brains of the insects, hardened them by means of 

 Betz's fluid (a mixture in equal proportions of sulphuric ether and 

 chloroform), and made thin slices of them. — Comptes Rendtu, Au- 

 gust 11, 1879, p. 378. 



