43 



cana^ which are greyish white in the living condition, also stain red in 

 the same manner. Hairs are present, of two kinds; (I) stiff, straight, 

 pointed hairs of the kind found all over the body ; these are scattered 

 sparingly over the cuticle covering various parts of the organ; (II) very 

 minute short and fine sensory hairs, confined apparently to the ridges 

 dividing the depressions of the sixth somite, and connected each to a 

 nerve filament. The hypodermis lying between the cuticle and base- 

 ment membrane is enormously thickened in the organs of both the 

 sixth and seventh somites. There is also a small isolated thickening 

 on the intersegmental membrane between the fifth and sixth terga, 

 perhaps the homologue of the organ in the various species of Peri- 

 planeta. The ridge and cirrus are formed as sharp folds of the cuticle, 

 hypodermis, and basement membrane, and transverse sections show a 

 similar folding of the hypodermis and basement membrane all along 

 the middorsal line of the sixth and seventh somites. The thickened 

 hypodermis contains the following elements ; (I) lying close under the 

 cuticle is a layer of small darkly staining nuclei, each belonging to a 

 narrow elongated cell which extends inwards about half way to the 

 basement membrane; (II) close to the basement membrane is a layer of 

 nuclei lying at varying distances from it, each large round and granu- 

 lar with a nucleolus ; these nuclei belong to large, elongated, granular 

 cells, which rest on the basement membrane, and at their inner ends 

 are enlarged and in contact with one another, but more externally they 

 narrow into tapering processes extending up almost to the cuticle, and 

 appearing to interdigitate with the cells of the outer layer; (III) inter- 

 spersed with these elements are numerous slender nerve filaments, with 

 elongated fusiform nuclei at intervals. They either end in the cuticle 

 in a manner not determined, or in minute hairs, and in the latter case 

 the filament either runs directly to the hair, or first swells out under 

 the cuticle into a small nucleated ganglion cell from which a delicate 

 filament is given off" to the hair. In some sections the filaments have 

 been observed springing from a nerve lying under the basement mem- 

 brane beneath the ridge of the sixth tergum. 



Want of leisure prevents me at present from working out the 

 structure and development of these organs more fully, but I hope to 

 do so later on, and any one who would be kind enough to send me in 

 the mean time living or well preserved specimens of different species 

 of Blattidae (other than Periplaneta orientalis and americana and 

 Blatta germanica) would render me a great service ^. 



1 It is possible that these organs may occur in other Orthoptera allied to Blat- 

 tidae, such as Mantidae and Acrididae. M. J. Kiinkel has described in the larva of 

 the hemipterous Cimex lectularius 3 odoriferous glands, each with paired openings 



