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POPULAR SCIENCE REVIEW. 
group ; the Conopidae, and the greater part ‘of the Muscidae Acalypterae 
having one thoracic and one abdominal centre, may form a second; the 
Syrphidae, with one thoracic and two abdominal centres constitute a third 
very natural group ; the Tabanidae and Stratiomyidae, with one thoracic and 
five abdominal masses, a fourth ; the Therevidae, which have two thoracic 
and five abdominal centres, and the Scenopinidae, with three thoracic and 
five abdominal masses, form parts of special groups; whilst a seventh 
section, having two or three thoracic centres, more or less confounded, and 
always six abdominal centres, includes the Xylophagidae, Empidae, Asilidae, 
Bonbyliidae, Bibionidae, Oulicidae, Tipulidae, &c. This proposed grouping 
will hardly be accepted by entomologists, although in some particulars it is 
very suggestive. 
The Cephalic Ganglia of Insects. — M. N. Wagner describes the structure 
and functions of the ring of ganglia surrounding the oesophagus in insects 
( Comptes rendus , August 11, 1879). According to him the suboesophageal 
ganglion has nothing to do with the general co-ordination of the movements 
of the insect ; it chiefly governs the organs of the mouth, and differs but 
little in its histological structure from the other knots of the ganglionic 
chain. The supra-oesophageal ganglia he regards as truly cerebral, and as the 
seat of nearly all the functions of the cerebral hemispheres of the vertebrata. 
Hence their structure is more complex, although they are constructed upon 
the same general plan as the other ganglia. In the middle they present 
bundles of nerve-fibres, whilst the nerve-cells chiefly occupy the periphery. 
Towards the centre of the ganglion there are three small groups of cells one 
above the other and communicating by numerous fibres. The foremost 
group has the closest relations with the convolutions (or horse-shoe bodies), 
which are particularly well-developed in the social Hymmoptera, the most 
intelligent of all insects, and the author states that the development of these 
parts is coincident with the intellectual development. Thus it is most re- 
markable in the worker ants and the worker bees, and less striking in the 
female ant and queen bee. These parts are rudimentary in the males. 
From the sides of the ganglia issue the lobes which go to the compound 
eyes. These are oval, and formed in the middle of short cylinders arranged 
in rows. These cylinders give origin to fibres which penetrate to the base 
of the brain. In the external part of the optic lobes these fibres intercross 
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 on the right side, 
and the inferior fibres become superior, and 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 eyes. This organization probably 
causes a perfect coincidence of all the optical impressions received by each 
eye. 
Nerves of the Proboscis of Dipt era. — M. Jules Kiinckel has examined 
into the terminations of the nerves in the proboscis of the Diptera 
(Assoc. Franq. Avancem. des Sci., 1878, p. 771). He remarks that the 
proboscis terminates in two valves, which, in repose, are laid against each 
other, but during suction are applied to the surface attacked so as to con- 
stitute a regular sucking cup. These valves represent the labial palpi. 
Their internal structure presents a peculiarity well known to microscopists ; 
