MtsceUaneous. (5o 



segments only, the protocerebron and doutocercbron, both of which 

 are provided with precesoph igeil commissures. The protocorebron, 

 whicli innervates tlie eves, is comparable to the protocerebron of the 

 Crustacea and Insects ; it is nevertheless to be observed that in 

 Limulus the pedunculate body attains truly colossal proportions. 

 The same organ, although considerably modified, is still recognizable 

 in the Arachnids, in which M. Saint-llemy has described it under 

 the name of the stratified organ ('' oir/cnie stratijte "). 



In Limulus and the Arachnids the dcutocerebron, instead of inner- 

 vating olfactory antennto, as in the Crustacea and Insects, performs 

 the same function for the clieliccraj, which are simply tactile appen- 

 dages, and so is not differentiated in view of special sensorial 

 perceptions. The tritocerebron is wanting in Limulus and the 

 Arachnids, and the first ganglionic mass which follows the dcuto- 

 cerebron is devoted exclusively to the innervation of the first 

 maxillii)ede or mandible*. 



The visceral nervous system of Limulus and the Arachnids is repre- 

 eented only by lateral ganglia, which, as in the case of the Insects, 

 derive their roots from the dcutocerebron ; the median ganglia are 

 wanting ; the absence of these centres is evidently correlated to that 

 of the tritocerebron. 



Finally, we may express the differences and resemblances pre- 

 sented by the different types of Arthropods as regards the organiza- 

 tion of the brain by dividing these animals into two great groups. 



The first of these, comprising the Arachnida and Limulus, is 

 characterized by the absence of the tritocerebron and the non- 

 differentiation of the dcutocerebron into an olfactory centre. 



The second, which embraces the Crustacea, Inseota, Myriapoda, 

 and Perijxttus, is characterized by the presence of a tritocerebron 

 and the differentiation of the dei'.tooerebron into an olfactory centre. 



This group may be itself subdivided into two sections, the first 

 containing only the Ciiistacea, which are provided with two pairs of 

 antinnit, the second embracing Myriapoda, Insecta, and Peripatus, 

 which possess a single pair of antennae. — Comptes Hindus Hebdo- 

 madiiires des Seances de la Societe de Biologie, n. s., t. iv. (May 6, 

 1802), pp. 354-357. 



On the Circulation of the Blood in young Sjnders. 

 By M. Mauckl Causakd. 



T have examined the circulation in young spiders belonging to 

 fifteen genera of Dipneumones, of which the following twelve tiave 

 been determined by M. Eugene Simon : — Dicti/na, 2'entina, Theri- 

 dioii, Epeira, Zilla, Micariosoma, Chiracanthium. Tcxtri.v, Clotho, 



* The rostrum of Arachnids is analogous to th'- labrura of Crustaci^a 

 and Insects, but it beLmgs to the second zouite ami is iniicrvaled by iLa 

 deutocerebroii. 



Ami. cf- -^f'tg. y. Hint. Ser. ti. To/, xi. 



