192 W. H. FURLONGE ON THE PULEX IRRITANS. 



they appear wholly unsuitable to the tentative, olfactory, and pro- 

 bably other sensorial purposes, served by the antenna? as ordinarily 

 placed in insects, and when to these considerations is added the 

 reflection that there is something so very suggestive of acoustical 

 purpose in the thin membranous plates, extending over deep 

 chambers in the head, as also in the laminated and apparently 

 tubular structure of the organ itself, and in the arrangement of the 

 long stiff seta3 stretching over it, so manifestly adapted to the con- 

 veyance of the vibratory impressions produced by sound, it is 

 difficult to resist the inference, that the organ, as a whole, is, at all 

 events mainly, one of hearing. It is, however, proper to remark, 

 that in hazarding this opinion, I submit it upon hypothetical grounds 

 only, as at present I have no proof to offer, of the existence of any 

 bodies homologous with the otilithes of the higher animals, such, 

 for example, as those bodies observed by our friend, Mr. Lowne, 

 in the halteres of the blow fly, which organs he has thereby 

 been enabled, with great probability of correctness, to identify as 

 the hearing organs of that insect. Until some such bodies, there- 

 fore, have been made out to exist in the antenna? of the flea, the 

 conjecture I have ventured to make as to their being hearing 

 organs must, despite all my reasons for the opinion, be confessedly 

 submitted as purely provisional and, indeed, hypothetical. 



The Mouth and its Tropin. — We now come to the considera- 

 tion of the mouth and the complex set of organs composing it. 

 These, it is by no means an easy matter to make out, in all their 

 details, in a perfectly satisfactory manner, and though I have devoted 

 much time to the investigation, I am doubtful whether I have been 

 able to apprehend, if even to see, all that really exists. The fol- 

 lowing, however, is the best description I am at present in a position 

 to offer of this beautiful apparatus. 



The mouth of the flea appears to be composed of nine distinct 

 parts or organs, viz. — 



Two maxilla?, two maxillary palpi, two labial palpi, f two man- 

 dibles, and the Iigula, or suctorial organ. 



The Maxilla? are attached to the lower frontal portion of the 

 head on either side, just within the margin of the headpiece, and 

 consist of two nearly triangular leaf-like plates of chitin, some- 

 what thick at their junction with the head, but gradually diminish- 

 ing in substance until they terminate in very thin, pointed extremities, 

 which project downwards. The maxilla? are not moveable, and ap- 



