'>34 M. F. Dalil on the Auditori/ and 



surface of the maxilla3 is found, when seen under a high 

 power from the surface, to be closely set with fine orifices. 

 In perpendicular section (fig. 4, go) we see beneath the 

 sieve-like integument a layer of closely approximated long 

 cones, shown, more highly magnified, in fig. 5. Where the 

 chitinous envelope has been slightly lifted in sectioning (as in 

 fig. 5) these cones contract a little at the end, and in conse- 

 quence they separate from each other, and thus at once show 

 that they do not form a coherent mass. 



In transverse section they exhibit a nearly regular poly- 

 gonal form. Fig. G shows (at a) such a transverse section of 

 the cones with the overlying integument. Here we see at 

 once that each three or four orifices correspond to a cone. The 

 cones consist of a finely granular mass (which reminds one of 

 the so-called olfactory cones of the Copepoda &c.). At the 

 bottom each of them contains a sharply defined nucleus, 

 beneath which the cone is constricted, and seems to pass into 

 a fine thread (fig. 5, y?), which unites it to a membranous plate 

 ( pi). The cones are enclosed by an extremely delicate mem- 

 brane, which emits small points into the pores of the integu- 

 ment. The membranous plate {pi) stretches over the whole 

 extent of the perforated plate, and is also continued beneath the 

 surrounding parts, where it bounds the matrix from within, 

 A tolerably strong nerve runs to this plate ; it branches off 

 from the palpal nerve. The fine threads which run to the 

 individual cones are therefore probably to be regarded as the 

 final ramifications of that nerve. 



If we now inquire into the origin of the organ, there can 

 scarcely be any doubt that the olfactory cones have originated 

 from cells of the matrix. For on the one hand there is no 

 other trace of any matrix under this part of the integument ; 

 secondly, the olfactory cells and the cells of the neighbouring- 

 matrix are in immediate contact ; and, thirdly, the membra- 

 nous plate, as already mentioned, is continued beneath the 

 matrix as an inner cellular membrane. 



The organ is universally distributed within the series of the 

 Araneaj. Nevertheless it is by no means equally perfectly 

 developed throughout. It has its finest development perhaps 

 in Pachygnathctj and for this reason I have drawn my figures 

 from preparations of this spider. 



In conclusion, we have before us the question as to what 

 function this peculiar organ may have. We might, perhaps, 

 in the first place, think of gland-cells, and, because it is in 

 the neighbourhood of the mouth, suppose it to be a salivary 

 gland, although even the general form does not seem to be 

 very much in favour of this view. But in fresh animals I 



