i io THE INTEGUMENTAL SKELETON OF THE IMAGO. 



of these views, and showed clearly that the skull is developed 

 from parts which do not undergo segmentation. My own 

 researches in the embryology of insects have sufficiently shown 

 me that the brain and head capsule of insects are also developed 

 from structures the procephalic lobes of Huxley which 

 undergo no segmentation. I am, indeed, convinced that there 

 are no prestomal segments in insects. 



'Viewed in relation to development, the brain in insects con- 

 sists of a central ventricle and two hemispheres, which are 

 themselves hollow. The central ventricle contains a transverse 

 and longitudinal commissure, the corpus centrale, and is con- 

 nected by its posterior wall with the median eyes or ocelli. 

 There is thus a close correspondence between the brains of 

 vertebrates and those of insects. The so-called antennal lobes 

 correspond to the olfactory bulbs, the central ventricle to the 

 third ventricle, and the ocelli to the pineal gland, or pineal eye, 

 where the latter is developed. The hemispheres are cerebral 

 lobes, and the pedunculated bodies are merely isolated convo- 

 lutions of the surface.' 



At that time I thought that such views would be regarded 

 as a return to ideas long laid aside, and I confess I was unable 

 to explain the position of the alimentary canal, which led me 

 to suspect that, however striking the analogy between the two, 

 it must be analogy only. 



Gaskell's Views. It was not until I had read Dr. Gaskell's 

 paper on the origin of the central nervous system in verte- 

 brates [45] that a more complete light was thrown upon the 

 whole subject. Still further confirmation is afforded by the 

 papers on the origin of vertebrates from a Limuloid ancestor by 

 Gaskell and Patten [47 and 48] quoted at the commencement of 

 this section. 



Both these authors bring a large amount of evidence to 

 show that the brain in the lowest forms of vertebrates corre- 

 sponds very closely with the cephalic nerve centres of the 

 arthropods. 



The most startling consequence of these views is Gaskell's 

 theory that the alimentary canal of the vertebrate is a new 



