344 E. T, NEWTON. 



brains was made by the publication of the memoir by E. 

 Berger in 1878 (' Arbeiten des Zoolog., Instituts zu Wien.,' 

 Bd. i, Heft li, p. 173). This memoir is largely occupied 

 with the description of the retina and the structures to be 

 found in the optic lobes of Arthropods. It is extremely 

 interesting to find that the peculiar oval bodies which Leydig 

 'figured as occurring in the optic lobe of Dytiscus (^Tafeln 

 z. Vergleich/ 1864), and were afterwards described and 

 figured by me as " lenticular bodies " in the eye of the lobster 

 ('Quart. Jour. Micro. Sci./ 1873, vol. xiii, p. 336), are to be 

 found in a more or less modified form in all the insects and 

 Crustacea described by E. Berger. The remarkable crossing 

 of the nerve-fibres between the retina and the lenticular 

 bodies is seen not to be peculiar to the lobster. The kidney- 

 shaped body, which is such a distinct part in the lobster's 

 optic ganglion, appears to be represented in the Squilla by 

 the body marked g in Berger's figure 32. The brains of a 

 number of insects are described, including examples from 

 the ISeuroptera, Coleoptera, Diptera, hepidoptera, Hymen- 

 optera, and Orthoptera, and in each of these the author 

 seems to have found the homologues of the mushroom bodies, 

 although in some — the Diptera, for example — they are very 

 rudimentary. Not a little important are the facts recorded 

 relative to the transverse commissures of the brain. It seems 

 to me somewhat doubtful whether the paired structures 

 which have been shown by several authors to be present in 

 the brains of Crustacea, are really the homologues of the 

 mushroom bodies of the insect's brain. Dietl has shown 

 (' Sitz. Kaiser. Akad„ d. Wissen.,' 1878, Band 77, p. 584) 

 that in the crayfish these bodies are connected with the 

 optic nerve, and he calls them optic lobes. Among the 

 Insecta this connection, if it exists, has yet to be demon- 

 strated. 



Dr. Flogel, in his paper already referred to (loc. cit.), takes 

 the Blatta brain as a typical form, and describes its internal 

 structure. Great stress is laid upon the persistent presence 

 in all orders of insects of that peculiar median laminated 

 structure, described by Dietl, which is now called by Flogel 

 the central body '^ Centralkbrperr In Blatta there is a pair 

 of mushroom bodies in each hemisphere. The cylinder of 

 fibres passing to the front of the brain is very large, and is 

 termed the anterior horn " VorderhornP The descliption 

 of the minute elements agrees with Dietl's observations 

 mentioned above. In the latter part of ihis paper the brains 

 of various insects are described, which have been taken 

 from the diff'erent orders, and a tabular scheme is given of 



