152 



T. NEWTON ON PREPARING A 



the outer or opposite end. The optic ganglion itself is a very 

 complex structure. The antennary lobes (al) consist of a number 

 of large rounded masses, -which have been called cells, but are 

 really made up of a network of fine fibres. Above the primary lobe 

 are seen the peculiar bodies, having the appearance of half-rings 

 (mb), which have been called convolutions, by Dujardin. (" Sur le 

 systemenerveauxdes Insectes," 1850. " Ann. Sci. Naturelles. Zool." 

 ser. 3, tome xiv., p. 195), and have been compared to mushrooms. 



FIG. 2. — Brain of Formica rufa, adapted from Leydig. — pi 

 primary lobe ; al, antennary lobe ; an, nerve to antenna ; op, optic 

 ganglion; fe, facetted eye; o, ocelli; mb, mushroom-bodies ; st, stems of 

 mushroom-bodies; c, cap of cells covering the mushroom-bodies; ma, 

 optical section of the anterior mass of nervous matter. 



Each of these mushroom-bodies is supported upon a stem (si) 

 which passes downwards into the primary lobe, where the two lie 

 close to each other, if they do not join. 



The exact form of these mushroom-bodies is not easy to be made 

 out from preparations such as that figured by Leydig, and, indeed, 

 the appearance presented by sections does not convey a very clear 

 idea of their form. 



In the middle of the primary lobe, as figured by Leydig, there is 

 a rounded mass, which he describes as a " giant nucleus " (ma), but 

 more recent researches have shown that Leydig was mistaken, and 

 that this appearance is really the optical section of a cylinder of 



