Io6 WHEELER. [Vol. VIII. 



of departure for further comparative studies. So far as my 

 own observations are concerned I am able to corroborate 

 Viallanes' results on nearly all important points. I must state, 

 however, that I have not followed the development into such 



detail. 



In the light of these researches a reconsideration of the 

 Coleopteran brain must be undertaken. Patten's description 

 of the Acilius brain ('88) and my description of the brain of 

 Doryphora ('89) need revision and alteration. We described 

 the organ (see my Fig. 72, PI. XIX) as consisting of three 

 segments, each of which was subdivided into a brain portion, 

 continuous with the ganglia of the ventral cord, an optic 

 ganglion portion and an optic plate portion. Between the 

 third brain and the mandibular segment, a segment was found 

 which I designated as intercalary. This segment is also 

 clearly seen in some of Patten's figures (Figs. 2 and 2"" s\ PI. 

 VII). Thus according to our account there were four preman- 

 dibular segments or seven segments in the entire head. Our 

 results were obtained almost exclusively from surface views — 

 by itself a defective method. But greater error was incurred, 

 it seems to me, in ascribing segmental values to the various 

 prominences of the optic ganglion and optic plate. 



In order to bring our observations into harmony with the 

 results obtained from a study of the Orthopteran brain, our 

 figures must be interpreted in a very different way from that 

 in which we chose to interpret them. Our first brain-segment 

 is probably no segment at all, but merely a slight elevation 

 often seen near the median line at the extreme anterior end of 

 the germ-band. Our second, third and intercalary segments 

 are equivalent to Viallanes' third protocerebral lobe, deuto- 

 cerebrum and tritocerebrum. The three divisions of the optic 

 ganglion are not parts of three segments, but the whole struc- 

 ture belongs to the protocerebrum, of which it forms the 

 first lobe. In the same way we cannot regard the optic 

 plate as trisegmental since it has no connection with the 

 deuto- and tritocerebrum but only with the optic ganglion. It 

 follows that the ocelli of Coleoptera are not originally formed 

 on different segments as Patten would have us believe, but 



