ON THE BRAIN OF THE COCKROACH. 341 



probable that we should here find the brain in a less special- 

 ised condition. The facts which have now been made out 

 show that, in the structure of its brain, the cockroach holds 

 a median position ; possessing as it does all the struc- 

 tures (excepting the ocelli nerves, unless, indeed, the white 

 spots near the bases of the antennae should prove to be 

 rudimentary ocelli) which have been described in other 

 insects ; but at the same time certain of these parts are 

 not quite so complicated and are, therefore, more easily 

 understood. 



It was not until I had nearly finished my own investiga- 

 tions, and was about to publish the results, that I saw the 

 memoir by Dr. Flogel (' Zeitsch. wissen. Zool.,' 1878, vol. 

 XXX, supple., p. 556), in which the internal structure of the 

 brain of Blatta is very fully described. On the whole the 

 results which I had obtained agreed with those of Dr. Flogel ; 

 but as my paper did not cover the same ground, and, more- 

 over, as little or nothing had appeared in British journals 

 on the minute structure of insects^ brains, it still seemed 

 desirable to publish the results of my own work. And, fur- 

 ther, as the Blatta's brain seems likely to be taken as the 

 type for comparison in future investigations, it is the more 

 necessary to have it fully illustrated, and the photograph of 

 one section only, which is all that is given by Flogel of the 

 Blatta brain, seemed to me quite inadequate for its proper 

 comprehension. Even with a series of sections and drawings 

 before me, it was by no means easy to get a clear conception 

 of the forms of some of the internal parts, and I therefore 

 "constructed a model from a series of sections {vide ' Quekett 

 Journal,' 1879, vol. v, p. 150), which gave me a far better 

 knowledge of these parts than I had found it possible to get 

 in any other way. 



The complicated internal structure of the brain of insects, 

 appears to have been first pointed out by M. Dujardin, and 

 attention is more especially directed to this, because the cor- 

 rectness and clearness of his descriptions do not appear to 

 me to have been sufficiently appreciated. 



M. Dujardin, in 1850 (' Ann. d. Sci. Nat.,' t. xiv, p. 195), 

 pointed out that in some insects there were to be seen upon 

 the upper part of the brain certain convoluted portions 

 which he compared to the convolutions of the mammalian 

 brain, and, inasmuch as they seemed to be more deve- 

 loped in those insects which are remarkable for their intelli- 

 gence, such as ants, bees, wasps, &c., he seemed to think 

 the intelligence of insects stood in direct relationship to the 

 development of these bodies. 



VOL. XIX. NEW SER. Z 



