178 Journal of Comparative Neurology. 



to the antenno-motor nerve are situated close to or in the lobe 

 on the anterior side of the brain. Fig. 39 represents a camera 

 drawing of the two fibers just described and also another from 

 the next section above them. 



The Dorso-Cerebral Fiber Tracts. 



THE CONNECTIONS WITH THE OPTIC LOBES. 



Tracts of fibers passing from the optic lobes into the cen- 

 tral part of the proto-cerebron were early recognized by Ber- 

 ger (78) and Bellonci (S2)i but the interpretations of these au- 

 thors are very largely incorrect. Viallanes (87,88) seems to 

 have described most of them much more correctly, and the 

 same may be said of Cuccati ( 88). so far as I am able, without 

 an actual study of sections of Soviomya, to homologize his results 

 with my own. Certain peculiarities are figured and described 

 by him that render a comparison difficult. 



Before describing the connections it should be noted that 

 the masses of fibrillar substance forming what are usually known 

 as the optic ganglia, but which are much more properly denom- 

 inated fibrillar masses, are seen in frontal or horizontal sections 

 treated by ordinary methods to be composed of two outer lay- 

 ers of densely staining masses, and very much resemble in form 

 two meniscus lenses placed one within the other. The space 

 between them is filled with a loose mass of fibers, and the whole 

 is so placed as to have its convex surface directed outward and 

 its concave surface inward. 



The inner of these masses lies in hexapods close against 

 the central proto-cerebron, being separated from it by a layer 

 of cells and a few bands of fibers. In other words there is no 

 optic nerve such as is found in the Crustacea. The attempts 

 by the earlier writers to distinguish an optic nerve were long 

 ago shown by Viallanes ( 87) to be more or less unsuccessful, 

 since there is not one but several connecting tracts. These 

 with the optic lobe sufficiently removed from the rest of the 

 brain, might, however, produce the homologue of the crustacean 

 optic nerve. 



