()2 Mt'sceVaneotts. 



poolojjicnl ]>oriod9. 8omo indications have boon ofForod in the 

 course of the essay, as shown above. The Mesozoic lloras in i)ar- 

 liciilar have yet to be carefully reviewed as tests of eliniato. Sug- 

 gestive remarks on fossil Forns and Conilers are then ofl'orcd ; and 

 the Aiithor says: — "Wo may expect that a closer study of the 

 (tcological tloras, not only from phylogenetic and anatomical, but 

 also from bioli)gieal points of view may enal)le us to penetrate further 

 into the life-conditions of those forests of which the Earth's crust 

 afl'oids us such numerous, though often too fragmentary, relics." 



The list of works referred to in the text, occui)ying pages 134- 

 1-J(J, well arranged and made serviceable with reference to the 

 numerous footnotes, is a welcome l)ibliograp}iy for ])ala3obotanists. 

 The Kssav has also a useful Index. Like other scientific works 

 issuing from the University Press at Cambridge, this is well [)rinled 

 on good paper. 



MISCELLANEOUS. 



C'omi>ar((tive Researches upon the Organization of the Brain in the 

 jn-incipal Grovps of Arthropods. By M. H. Viallauks. 



I HAVE the honour of commur.'icating to the Societe do liiologio 

 the principal results of researches Avhich I have been conducting for 

 several years upon the organization of the nervous system of 

 Arthropods, and of which I have hitherto only i)ublished detached 

 fragments, some in the ' Annales des Sciences XaturellOs ' and the 

 rest in the ' Comptes Rcndus do TAcademie des Sciences.' 



Or<jamz(ttion of the Brain of Insects. — In the Insects the brain is 

 formed of three segments corresponding to the first three cephalic 

 zonitcs. The first segment, or 2^^'otocerehron, innervates the eyes ; 

 it is the seat of the visual perceptions, while the psychic centres also 

 reside in it. The second segment, or cleutocercbron, innervates the 

 antenna) ; it is the seat of the olfactory perceptions. The third 

 segment, or tritocerehron, innervates the labrum and the initial 

 portions of the digestive canal ; in it is situated the centre of the 

 gustatory sense. 



Before entering further into detail as to the constitution of the 

 cerebral segments, it may be mentioned that the first two are 

 entirely ])recEsophagcal, that is to say that the commissures which 

 unite their symmetrical portions are situated in front of the 

 asophagus. In the case of the third segment the conditions are 

 different ; here all the commissural fibres ])as8 behind the oeso- 

 phagus, where they constitute the commissure known under the 

 name of the transverse comniissnre of tJie o-sapJiatjeal rimj. 



The protocerebron is composed of a pair of lateral masses termed 

 optic ganglia and of an intermediate median mass. The constitu- 

 tion of the optic ganglia is most remarkable and most constant; 



