THE PROBOSCIS. 49 



Between each pair of false tracheae the surface of the lobes is marked by 

 a pair of wavy lines ; these are folds of the integument, and disappear 

 when the membrane between the false tracheal channels is stretched. Four 

 or five nipple-shaped papillae project from the surface, between each pair 

 of wavy lines, and nerve filaments terminate in them ; they are probably 

 organs of taste. The disposition of these parts is shown in section, in 

 Plate IV, Fig. 3. 



A row of cells around the margin of the lobes are hardened into little 

 square plates ; these are developed in the membranous protoderm ; several 

 other, but less developed, rows of a similar nature extend towards the 

 back of the lobes. 



The mesoderm consists of beautiful nucleated pigment cells, filled with 

 a bright orange-colored pigment ; in the mature insect these are united into 

 a continuous membrane ; their nuclei become apparent on the addition 

 of a little acetic acid. 



The back of the lobes is covered with hairs, which form a fringe aroun^ 

 its disc. The endoderm consists of numerous spherical cells, containing 

 granular nuclei, and the bulbs of these hairs, with a plexus of nerve loop g 

 distributed to them, from the terminal branches of the great nerve of th e 

 proboscis. A group of recurved hairs with a similar plexus of nerve loops 

 is situated on each side of the second joint, near its anterior extremity. 



The false tracheal channels are partially surrounded at their orifices by 

 the curved extremities of the chitinous pillars which support them upon 

 the anterior border of the mouth. Closely connected with the points of 

 these, and immediately beneath the integument, is a tendinous looking 

 band of dense tissue, which extends the whole length of the fissure between 

 the lobes of the proboscis. A round cord of similar tissue arises partly 

 from this band, and partly from the point of the chitinous pillar, on either 

 side of each false tracheal channel. The pair which arise from each pair 

 of points unite and form a thicker round cord, which runs outwards towards 

 the margin of the lobe, near which it is inserted into a thickened ridge of 

 chitine, connected with the anterior extremity of the anterior process 

 of the mentum, at right angles to it. The purpose of these cords 

 seems to be to connect the extremity of the anterior processes of the 

 mentum with the margins of the fissure between the lobes, which is pro- 

 ably kept closed by the elasticity of the pillars which support the orifices 

 of the false tracheae, and which is opened by the muscles attached to the 

 anterior processes of the mentum, through the agency of these tendinous 

 bands. If these processes of the mentum acted upon the margin of the 

 fissure by drawing upon the integument of the lobe, the margin of the 

 sucker, formed by the union of the lobes, would have been disturbed in 

 order to open the fissure; whilst, by means of these bands, the anterior 

 process of the mentum not reaching the margin of the lobe, acts directly 



