ON THE BRAIN OF THE COCKROACH. 351 



a convex surface outwards (figs. 8 and IT). Quite towards 

 its upper end the peduncle divides into two parts, one of 

 which joins the outer (fig. 13), and the other the inner 

 calix. 



With regard to the histology of these structures I am now 

 able to give the following particulars : — The upper part of 

 the peduncles, where they join the calices, shows a most 

 definite fibrous structure even with a low power of the 

 microscope, and this is seen extending downwards more or 

 less distinctly as far as their junction with the traheculce. 

 The trabecule themselves and the cauliculi present only a 

 finely granular or dotted appearance unless examined with a 

 high power. Under a -^V immersion both these parts exhibit 

 a fine reticulation, the meshes of which have, perhaps, a 

 diameter of — i-u"o77 of ^^ inch, but they are extremely diffi- 

 cult to define. The peduncles , with the same amplification, 

 show a similar network, but not quite so fine, and the 

 meshes are more elongated (fig. 14), especially towards the 

 upper part, and it is this which gives it a fibrous appear- 

 ance. It is, in fact, a bundle of fibres which freely anas- 

 tomose with each other. The peculiar system of bent lines, 

 mentioned by Flogel, is to be seen in horizontal or oblique 

 sections, where the cauliculi ']oh\ the trabecula;, and in frontal 

 sections where the latter join ihe peduncles (figs. 7, 8^^.). 



The manner in which these remarkable nervous structures 

 are connected with the other parts of the brain and nervous 

 system have yet to be established. The only parts at 

 present known to be connected with them are the corpora 

 fungiformia. The nervous fibres which surround them on 

 all sides seem to be merely in close apposition, and not to be 

 really united with them. Towards the back of the brain, 

 where the traheculce become reduced in size, they also 

 become less and less clearly separated from the surrounding 

 parts, and it seems possible that there is some connection in 

 this region. Possibly some of the fibres which extend down- 

 wards from thejarge cortical ganglionic cells at the back of 

 the brain (fig. 10) join the traheculce, but I have been unable 

 to trace any such connection. One would naturally expect 

 that such large and important parts of the brain, as the 

 trahecidiB and its appendages, the cauliculi, peduncles, and 

 corpora fungiformia, would be very obviously connected with 

 the rest of the brain, or, at least, that we should find fibres 

 extending from it into the oesophageal commissures. 



Corpora fungiformia. — There are two of these bodies in 

 each hemisphere, an inner and an outer one, both extending 

 from near the front almost to the back of the brain. Each 



