Miscellaneous. 63 



they are composed of a series of tlirco ganglionic masses united to 

 one another by decussating fibres. The median protocerebral mass 

 is formed of a pair of lobes, which are intimately fused together and 

 contain in their interior — (1) the pedunculate bodies, which are the 

 scat of the psychic functions ; (2) the central body, the organ 

 whither fibres coming from all points of the brain converge ; (3) the 

 pons of the protocerebral lobes, a portion discovered by myself, the 

 significance of which is as yet unknown. 



The deutocerebron is composed of a dorsal portion, the structure 

 of which has nothing particularly noteworthy about it, and of two 

 olfactory lobes, which are highly differentiated in view of their 

 special functions, and are characterized especially by the presence 

 of organs known under the name of olfactory glomerules. The 

 olfactory lobes, whence the sensory fibres of the antennary nerve 

 originate, are united to the optic ganglia and to the pedunculate 

 bodies by fibres which decussate in the median line ; this connexion, 

 which is absolutely constant, seems to be bound up with physio- 

 logical necessities. Besides the antennary nerves, the doutocercbrou 

 gives origin to a pair of tegumentary nerves and to a pair of roots 

 destined for the visceral nervous system. 



The tritoccrebron is represented in the Insect solely by a pair of 

 ganglionic masses, which we will designate oesophageal ganglia ; 

 these are separated from the median line and united to one another 

 behind the oesophagus by the transverse commissure of the oesopha- 

 geal ring. Each of the oesophageal ganglia gives rise by means of 

 a common trunk to a nerve, which is destined for the labrum, and 

 to a root of the visceral nervous system. 



In the Insects the visceral nervous system is composed — -(1) of a 

 series of three median ganglia, which are connected with one 

 another, and of which the first, known by the name of the " frontal 

 ganglion," is united to the oesophageal ganglia by a pair of roots, 

 which are often double ; (2) of a pair of lateral ganglia*. Each of 

 these latter is connected, on the one hand, with one of the median 

 ganglia, and on the other with the deutocerebron, by means of a 

 nerve-root which has already been mentioned. 



The brain of the Myriapods is precisely similar to that of the 

 Insects in structure. But the visceral system of these animals 

 exhibits a remarkable condition, for it preserves throughout the 

 whole of life certain characters which in the Insect are only found 

 in the course of embryonic development. 



For our knowledge of the cerebral structure of Peripatus we are 

 indebted to the researches of M. Saint-Bcmy f ; it is connected in 

 the closest manner with that of Myriapods and Insects. 



* The lateral ganglia are generally each divided into two little masses, 

 termed by M. Blanchard the gauglia of the vessels and trachese ("gan- 

 glions angieu at tracheen"). 



t M. Saint-Remy has published (Arch. Zool. exp. vol. 'in.bis) a most 

 conscientious paper upon tlie structure of the brain of Arachnids, Myria- 

 pods, and Peripatus; this has been of great assistance to me 



