Miscellaneous. 65 



segments only, the protocerebron and deutoeerebron, both of which 

 are provided with preoesophiigeal commissures. The protocerebron, 

 which innervates the ej'ea, is comparable to the protocerebron of the 

 Cruslacea 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-Remy has described it under 

 the name of the stratified organ (" organe stratifie "). 



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

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

 the same function for the cheliceras, which are simply tactile appeii- 

 dages, and so is not diifei-entiated in view of special sensorial 

 perceptions. The tritocerebron is wanting in Limulus and the 

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

 eerebron is devoted exclusively to the innervation of the first 

 maxillipede or mandible *. 



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

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

 derive their roots from the deutoeerebron ; the median ganglia are 

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

 of the tritocei"ebron. 



Finally, we may express the differences and resemblances pre- 

 sented by the difl:erent 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 deutoeerebron into an olfaetGry centre. 



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

 and Peripatifs, is characterized by the presence of a tritocerebron 

 and the differentiation of the deutoeerebron into an olfactory centre. 



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

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

 antcnnoe, the second embracing ilyriapoda, Insecta, and Peripntus, 

 which possess a single pair of antennas. — Comjytes Hindus Ifehdo- 

 rnadaires des Seances de la Societe de Bioloc/ie, n. s., t. iv. (May 6, 

 181)2), pp. 354-357. 



On ihe Circidatiov of the Blood in young Spiders. 

 By M. Marcel Causakd. 



T have examined the circulation in young spiders belonging to 

 fifteen genera of Dipneumones, of which the following twelve have 

 been determined by M. Eugene Simon : — Dicti/mi, Tentana, Theri- 

 dion, Epeira, Zilla, Micariosoma, Chiracanthium. Tcxtriv, Clotho, 



* The rostrum of Arachnids is analogous to the labnim o^ ( 'rustacea 

 and Insects, but it bfluugs to the secouil zonite and is innervated by tho 

 deutoeerebron. 



.1;///. (i- Ma(/. X. I lust. Ser, G. T y/. xi. 



