Literary Noticpzs. xxxiii 



and the Pliahingidd- it is tiiiite comiilex. The optic lobe gives origin to 

 a pair of nerses corresponding to one kind of ejes; the nidulus, how- 

 ever, contains two nervous centres, corresponding to two kinds of eyes. 

 The structure of the rostro-mandihular ganglion is more simple and 

 more uniform. It consists of a nervous mass penetrated bj the alimen- 

 tary canal. The supra-oesoph^geal portion is composed of three niduli; 

 one small rostral nidulus and two large mandibular niduli. The rostral 

 nidulus lies cephalad to the CESophagus. From it an unpaired median 

 nerve passes to the rostrvmi. This nerve is the homologue of the nerve 

 that passes to the upper labia of insects, mjriopods and crustaceans, 

 The mandibular niduli are laterally situated. They serve to enervate 

 the mandibles. In the Phalangidm there is a single pair of mandibular 

 nerves; in the Araneidce, also, there is only a single pair of nerves, but 

 each nerve is bifurcate; while in the Scorpionidcr we find two pairs of 

 nerves. 



5. In Peripatus the brain is not obviously segmented, but in the 

 remaining tracheate arthropods it is composed of a cephalic and a 

 caudal region. The cephalic portion is pre-oral, and is evidently 

 homologous to both the protocerebron and the deutocerebron of insects, 

 myriopods and crustaceans. The caudal region is shown by both em- 

 bryology and anatomy to be composed of the ganglion of the first post- 

 oral somite. It is probably homologous to the tritocerebron of insects, 

 myriopods and crustaceans. 



6. The roots of the unpaired visceral nerves of myriopods and the 

 paired sympathetic nerves of the Araneidce and Paripatus appear to 

 have the same morphological value and to correspond to the unpaired 

 visceral nerves of insects and crustaceans. 



7. Among all the tracheate arthropods that possess eyes the first 

 cerebral ganglion contains a more or less differentiated organ (the optic 

 lobes), which is interposed between the deeper regions and the retina. 

 Its function appears to be the elaboration of visual impressions. The 

 structure of this organ is not necessarily constant for the same kind of 

 eye, and variations in its structure apparently greatly modify the phe- 

 nomena of vision. Indeed, modifications of this body appear to be of 

 more importance than variations of the eye itself. The remainder of the 

 cerebral ganglion is not entirely concerned with vision; it is psychical 

 in function. The structure of these regions is greatly influenced by 

 their physiological role. [c. h. T.i 



The Nervous System of Copepods.(I) 



The brain of Diaptomus, according to this author, is an irregular 

 body, consisting of a central mass of " dotted substance " surrounded by 

 a layer of cells, varying in thickness at various points. The primary 

 brain consists chiefly of " dotted substance," the secondary of nerve 



I M. .1. Ri( MAIM). Bull. Soc. ;^ool. France XV, iSqr. 



