864 KECOKD OF CURRENT RESEARCHES RELATING TO 



of a single larval ganglion into a number in tlie adult, as in Voliicella. 

 xi. In cases of a single thoracic ganglion in Hemiptera, tliis cor- 

 responds to the two last thoracic and all the abdominal ganglia, 

 xii. Lepidoptera have four abdominal, and either two or three 

 thoracic ganglia. 



Cephalic Ganglia of the Insecta.* — M. N. Wagner points out the 

 supra-oesophageal ganglia are the seat of almost all the functions 

 which are performed by the cerebral hemispheres of the Vertebrata — 

 they contain the organs of perception, of memory, and of intelligence. 

 In correlation with this they present a more complicated histo- 

 logical structure than the rest of the ganglia of the insect's body, 

 although they are formed on the same general plan. The nerve-cells 

 occupy the periphery, and the bundles of nerve-fibres the central 

 portion ; towards the centre of the ganglion there are to be found 

 three groups of small cells, set one above the other, and connected by 

 a large number of fibres. The most peripheral group may be con- 

 sidered as having the most intimate connection with the horse-shoe- 

 shaped convolutions, which are particularly well developed in the 

 social Hymenoptera, which are the most intelligent of all the insects ; 

 and it is to be noted that the degree of development of this region is 

 to be correlated with the development of the intellectual powers ; for 

 example, if we take the bee, we find these parts to bo better developed 

 in the workers than in the queen-mother, while in the males they are 

 quite rudimentary, M. AVagner concludes that the sexual life, and 

 above all the production of ova and sperm, is opposed to the develop- 

 ment of these organs. 



The crossing of the nerve-fibres which pass to the eyes is not to 

 be compared with the " ojitic chiasma " of the Vertebrata, as it only 

 applies to the constituent parts of the lateral compound eyes ; at the 

 same time this crossing of the fibres probably produces a complete 

 coincidence in each part of the composite eye. 



The prejDarations studied were previously hardened in Betz's 

 liquid, made of equal parts of sulphuric ether and chloroform. 



Brain of the Cockroach. t — Mr. E. T. Newton gives an account 

 of his researches on the minute structure of the brain of Periplaneta 

 orientalis. 



After an abstract of previous work on the subject, Mr. Newton 

 describes the external anatomy of the brain as made out by sections, 

 and the nerves proceeding from it. Of these he gives a very exact 

 and detailed description, many of the nerves having been observed by 

 him for the first time. 



The section of the paper treating of the internal structure of the 

 brain cannot readily be abstracted, and we must refer the reader to 

 the original source, where the description is by no means long. Mr. 

 Newton deserves the thanks of comparative anatomists for proposing a 

 consistent nomenclature for the various structures, hitherto only 

 known by Flogel's vernacular terms. That author's " Balk 



* ' Comptes Kenchis,' Ixxxix. (1879) p. 378. 

 t 'Quart. Jouru. Micr. Sci.,' xix. (1879) p. 340. 



icn 



