6 io THE SENSES AND SENSORY ORGANS. 



Lee, in 1885 [299], investigated these organs in the Blow-fly, 

 and came to the conclusion that the chordotonal organs of the 

 halter are not in relation with the pores of the basal and scapal 

 plates, but form a special organ. 



According to Lee, the basal papillae open externally by a 

 narrow funnel which is sometimes round, sometimes slit-like ; 

 at the bottom of the funnel is a cushion, which is perforated 

 by a fine fibril given off by a subjacent bipolar ganglion cell. 

 In favourable objects Lee claimed to have seen a very fine, 

 often bent, hair projecting from the cushion through the 

 funnel. The scapal papilhe were regarded by Lee as similar 

 to the basal papillae, but more difficult to investigate, owing to 

 the more complex sculpturing of the cuticular layer. 



\Yeinland [300] describes the scapal papillae as opening 

 externally by a slit which communicates with a cavity con- 

 taining a cone-like nerve terminal. The basal papillae differ, 

 however, according to him, in having a kind of chitinous 

 operculum closing the orifice of the cavity which contains the 

 nerve terminal. I have made the most careful and repeated 

 examination of the organs in question, and although I have 

 seen all the appearances figured by Weinland at different times, 

 I do not think his conclusions correct. Other appearances 

 which are frequently seen are quite inconsistent with the view 

 he takes, and he has, I believe, fallen into error in mistaking 

 oblique sections of fragments of the halter for sections vertical 



DKSCKIPTION OF PLATK XLIII. 



Tin; halter and tympanic organ of the Blow-fly. 



Kit:. I. A longitudinal section of the scabellum and part of the scape of a halter. 

 b, basilar membrane separating the canal of the scape from the chordotonal 

 organs ; c t , superior, and r\,, inferior canal of the scape ; c/t, Lee's chordotonal 

 organ ; at, cupola ; ;/, nerve ; /, tubercle at the base of the halter, seen with a 

 ,'.. oil immersion objective. 



FlG. 2. A transverse section through the scabellum. (7, anterior ; s, superior, and 

 /, posterior surface ; c, a portion of the inferior canal ; f l r,, a portion of the 

 superior canal ; c/i, small chordotonal organ ; //, to >i 4 , branches of the nerve ; 

 ., an inflection of the external integument, seen with a ,'. 2 oil immersion objective. 



FlG. .5. The right tympanic fissure of a Blow-fly; </, sclerite in the floor of the 

 hure; />, propterygium of the wing; s</ , squama or great wing scale; si/a, 

 M[uamula ; t :, tympanic sclerite in the upper part of the membrana tympani ; 

 7.', part of the wing ; A, deltoid, and r, tau of the wing. 



