and on the Function of the Antennce in Crustacea. 41 



In the Anomoura, Macroura, and all below, the antenna gra- 

 dually increases at the base. In the Brachyura this increase is 

 immensely developed in the first or basal articulation. Exami- 

 ning this organ in the larva^ I thought I observed v^hat I took to 

 be an otolithe*; this led my attention to the same in the adult 

 Brachyura, and there I found, upon breaking open the basal ar- 

 ticulation, what appeared to be an imperfect kind of cochlea. 

 Afterwards, in company and with the assistance of my friend 

 Mr. Howard Stewart, we were enabled to trace distinctly the 

 nerve which supplied this antenna directly to the centre of the 

 cochlea (for such I believe it is), as I feel convinced that the 

 upper antennse are auditory organs. 



But since the general opinion up to the present time has been 

 that they are olfactory and not auditory, and as the external an- 

 tennae are invariably considered as auditory and not olfactory, I 

 shall withhold any further discussion until those organs have 

 been described. 



In the lower forms of Podophthalmia, as also in the Sessile-eyed 

 Crustacea, the basal joint of the antenna is not enlarged, neither 

 have I been enabled to find any structure answering to the 

 internal cell ; on the other hand, the whole organ increases in 

 length, as if to gain by external surface what is lost by internal 

 development. 



Among the land Crustacea this antenna is obsolete, and in 

 Ligia and other amphibious marine ones it is rudimentary. 



The Inferior or External Antenna. 



These are borne upon the third ring, and are among the most 

 constant organs present. One of these antennje is formed of a 

 peduncle consisting as a general law of five articulations and a 

 filament, generally multiarticulate and very long; these are 

 sometimes anchylosed together so as to be even as fcsv as a single 

 articulation. 



The five joints of the peduncle are all distinct in the Macroura. 

 In Amphipoda the first and second are closely associated, but 



* In Macroura, Dr. Farre states that he found sand deposited in the base 

 of the internal antenna, whieh he assumes to act the part of otoHthes ; this 

 the author has failed to find, and, from the fact that the membrane over the 

 orifice spoken of b}' Dr. Farre is imperforate, thinks it probable that the 

 specimen examined by that observer must have been injured. 



It may be that in this communication sufficient justice is scarcely done 

 to Dr. Farre's researches, since the short abstract published in the ' Annals ' 

 for 1843 has been the only means the author had at his disposal to become 

 acquainted with them. But if, as he thinks. Dr. Farre's researches 

 on the Macroura corroborate his on the Brachyura, then the evidence is 

 strong against the generally received opinion of naturalists and physiologists, 

 including among them Edwards and Siebold. 



