578 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The relation between the geometrical cell and the interior and exterior 

 spheres may possibly have some bearing on the question of the formation 

 of the actual cells. 



Brain of Vespa crabro and V, vulgaris.* — M. H. Viallanes, in the 

 fourth of his memoirs on the structure and histology of the nervous centres 

 of Articulata, deals with the brain of Vespa crabro, and F. vulgaris. He 

 divides the brain into three great regions, which he calls protocerebrum, 

 deutocerebrum, and tritocerebrum (" protocerebron," &c.) ; the first of 

 these consist of the two optic ganglia, the three ocellar ganglia, and the 

 median protocerebrum. The optical ganglion is almost identical in consti- 

 tution with that of Libellula, and consists of post-retinal fibres, ganglionic 

 layer, external chiasma, external medullary mass, internal chiasma and 

 internal medullary mass. The optic nerve connects the ganglion with the 

 median protocerebrum, and is composed of four perfectly distinct bundles, 

 two of which are superior and two inferior ; of the latter, one is very large, 

 and is formed of two distinct cords. The ocellar ganglia are found beneath 

 the ocelli; each consists of a mass of dotted substance, which is fairly 

 homogeneous, and has connected with it small nervous cells, in which the 

 protoplasm is much reduced. The median protocerebrum is made up of two 

 pedunculated bodies, two cerebral lobes, and a central body. The first of 

 these consists of the internal and external calyx, together with the stalk : 

 the elliptical calyces have their walls formed of a thick layer of dotted 

 substance, and both their internal and external surfaces are invested by a 

 thick layer of small nerve-cells. Five parts are to be distinguished in the 

 peduncle, the stalk of which is united to the substance of the cerebral lobes 

 by two large fibrous bundles. The central body, although consisting almost 

 exclusively of dotted substance, has a complex structure ; it enters into 

 relation with nearly all the constituents of the protocerebrum, fibres extend- 

 ing to the cortex, to the calicos, to the cerebral lobes, the oesophageal 

 commissure, and the olfactory lobes. 



The two cerebral lobes are intimately connected beneath the central 

 body ; they are essentially formed of dotted substance, among which are a 

 large number of fibrous bundles with definite courses ; the connection between 

 the lobes is effected by two commissures, one superior and one inferior ; the 

 oesophageal commissures are very voluminous and are continuous with the 

 cerebral lobes ; they also consist of a very homogeneous dotted substance, 

 among which are a few bundles of well-marked fibres. Attached to the 

 protocerebrum is a special organ which the author calls the wings of the 

 cerebral lobe ; it is entirely formed of dotted substance, and is everywhere 

 surrounded by ganglionic cells. 



The cerebral lobes are themselves everywhere surrounded by nerve-cells 

 arranged in layers, which are thickest behind and in the median region ; the 

 prolongations which they give off pass to the central body, to the stalk of 

 the pedunculated body, and to the olfactory lobe, as well as to the cerebral. 

 The deutocerebrum is represented by the two olfactory lobes, each of which 

 has the form of a rounded projection, attached by a short stalk to the 

 anterior face of the corresponding oesophageal commissure. The structure 

 is very characteristic ; the central part is formed of somewhat loosely 

 arranged dotted substance, and the cortical consists of a layer of olfactory 

 glomeruli; each of these last has the appearance of a small sphere of 

 dotted substance, and is united to the central part of the lobe by a short 

 peduncle which is formed of the same substance. The outer face of the 

 olfactory lobe is invested by a thick layer of small cells altogether similar 



* Ann. Sci. Nat, ii. (1887) Ait. No. 1, 100 pf.., 6 pis. 



