342 E. T. NEWTON. 



The form of these structures is described by the same 

 author as being, when fully developed, as in the bee, like a 

 pair of discs upon each side, each disc being folded together 

 and bent downwards before and behind, its border being 

 thickened and the inner portion radiated. By very careful 

 dissection he found these bodies to be connected on each 

 side with a short pedicle, which bifurcates below to end in 

 two tubercles. One of these tubercles is directed towards the 

 middle line and approaches, but does not touch, the corre- 

 sponding process of the opposite side. The second tubercle is 

 directed forwards and is in close relation to the front wall 

 of the head, being only covered by the pia mater. These 

 convoluted bodies and the stalks upon which they are mounted 

 are compared by Dujardin to certain kinds of mushrooms, 

 and this idea has been retained by more recent writers on 

 the subject. 



The physiological experiments of Faivre in 1857 (' Ann. 

 d. Sci. Nat.,' t. viii, p. 245) upon the brain of Dytiscus in 

 relation to locomotion, are of very considerable interest, 

 showing, as they appear to do, that the power of co-ordinating 

 the movements of the body is lodged in the infra-oesophageal 

 ganglia. And such being the case, both the upper and 

 lower pairs of ganglia ought to be regarded as forming parts 

 of the insect's brain. 



Dr. Franz Leydig, in 1864 {' Vom Ban des thierischen 

 Korpers,' &c.), entered fully into the structure of the nervous 

 system of insects, and described the histology of the various 

 parts of the brain. The method of preparation which he 

 adopted Avas to preserve the insect in absolute alcohol, 

 then to remove the brain, and render it transparent with 

 dilute potash solution, or glycerine. As regards the general 

 structure of the so-called mushroom body and its stem, 

 Leydig makes little advance upon what was done by 

 Dujardin, but, in consequence of his method of preparation, 

 as it seems, was misled into describing as a giant nucleus 

 upon each side of the middle of the brain, the peculiar mass 

 of nervous matter, v/hich Dujardin had correctly described 

 as a process extending forwards to the front surface of 

 the brain. 



In 1875 Dr. Rabl Eiickhard C Archiv. f. Anat. u. Phys.,' 

 p. 480), described the structure of the brain of the black 

 ant {Camjjonotus Ugnipordus), adopting chiefly the method 

 of preparation made use of by Leydig. He was enabled to 

 make out the head of the mushroom body with its stalk j 

 he also saw the appearance described by Leydig as a giant 

 nucleus, but believed it to be the optical section of cylindri- 



