154 Proceedings of the Royal Physical Society. 



falsity. I shall again have to speak of the actual nature of 

 the contents of the setse. 



Leydig, again, writing iu 1877/ in describing the antennae 

 of Gammarus, enters at some length into the question of the 

 functions of the various forms of setae in this and other 

 Crustacea. He describes and figures somewhat roughly, as 

 " gewohnliche Borsten/' setae closely resembling the tactile 

 setae in Astacus ; but in opposition to De Eougemont, whom 

 (p. 230) he quotes, and who regards these as tactile setae, 

 Leydig accepts the second variety — the " Fiederborsten " — 

 as tactile, and adduces in evidence his own and Weismann's 

 researches on the larva of Corethra phcmicornis:^ I shall 

 have more to say on this point when discussing the relations 

 of the various forms of setae. 



Vitzow ^ offers incidentally some remarks on the setae. 



Jourdain's paper* need only be mentioned to call attention 

 to the fact that on p. 417 he talks of the " different varieties 

 of setae considered to be tactile." 



As regards other A«thropods, I may cite Jobert, who ^ 

 devotes a small portion of his paper to the tactile apparatus 

 in the mouth-parts of various insects, and shows that there 

 are tactile end-organs very similar to those I am about to 

 describe. He seems, however, to have misunderstood the 

 nature of the connection between the end-bulb and the 

 tactile setae, since, in opposition to Laudois, who maintains 

 that the filament which unites the two is nervous in its 

 nature, Jobert holds that it is a slender, chitinous tube, 

 the hollow in whose interior is continuous with that of the 

 seta, and which " serves to communicate to the interior of 

 the nervous organ the impressions received from outside." 

 He also gives the literature of the sense of touch in insects 

 up to that date. 



1 Ueber Ampliipoden unci Isopodeii, Zeitschr., fur Wissensch. Zool. xxx., 

 Suppl. 1878. 



2 Leydig, Zeit. f. Wiss. Zool., Bd. iii., 1851 ; Weismann, do., Bd. xvi., 1860. 



3 Structure et i'ormation des teguments des Crustaces decapodes Arcli. de 

 Zool. exper. et gener., Tomex., No. 4. 



^ Keclierclies sur les polls a batonnet de I'antenne interne des Crustaces,. 

 Journ. de I'Anat. et de la Physiol., Tome xvii., 1881. 



5 Etudes sur les organes du toucher, Ann. Sc. Natur. (5), vol. 16, 1872. 



