PECULIAR SENSE 0?GAN IN SCCTTIGEEA COLE OPTR ATA. 199 



DESCRIPTION OF PLATE XX, 



Illustrating Mr. F. G. Heathcote's Paper " On a Peculiar Sense 

 Organ in Scutigera coleoptrata, one of the Myria- 

 poda." 



Letters used in all the Figures. 



m. Mouth, f. Furrow in cLitin. e. o. External opening of sense organ. 

 0. Sense organ, mxl. 2nd maxilla.' N. Nerve, s. e. Sense epithelium, 

 h. Chitinous hairs, hy. Hypodermis. p. Pouch. Ir. Lateral recess. M.r. 

 Median recess. hi. Lateral ventral lip. Mil, Median dorsal lip. ch. 

 Chitin. Bi. Bifurcated end of cell at top of median recess, oe. Outer 

 end of cell. Ih. Base of chitinous hairs projecting into interior, bp. 

 Basal part of chitinous hair. fh. Free end of hair. 



Fig. 1 was drawn for me by Mr. Chapman ; all other figures were drawn by 

 myself with the aid of Zeiss's camera lucida. Fig. 2 is combined from three 

 sections. 



Fig. 1. — Ventral view of head of Scutigera coleoptrata. The sense 

 organ is seen through the chitin. m. Mouth, f. A furrow in the chitinous 

 exoskeleton, marking out two irregular areas just in front of the organ, e o. 

 Opening of organ to the exterior, o. Organ seen through the chitin. oc. 

 Eye. mxl. 2nd maxilla. 



Fig. 2. — Transverse section through the organ, showing the nerve {N.), sense 

 epithelium {se.), chitinous hairs {h.), hypodermis {hy.), median recess {Mr.), 

 and lateral recesses (br.) ; also the two pouches {p.). (Zeiss's c c objective.) 

 Owing to the action of the reagents used the sensory epithelium has shrunk 

 away from the chitinous lining of the sac. Ivl. Lateral ventral lip. Mdl. 

 Median dorsal lip. 



Fig. 3. — Transverse section through the region of the lateral recess, show- 

 ing the transition from the hypodermis to the sensory epithelium, hy. Hypo- 

 dermic cells, se. Sense cells, br. Lateral recess, ch. Chitin. h. Chitin- 

 ous hairs projecting into the pouch. Ivl, Lateral ventral lip of pouch. 

 (Zeiss's F objective.) 



Fig. 4. — Transverse section, taken so as to show the hypodermic cells {hy.) 

 joining the sense cells {se.) in the region of the median recess. (Zeiss's i 

 objective.) hy. Hypodermic cells, se. Sense cells, ch. Chitin. 



Fig. 5.^Transverse section through the anterior part of the organ, show- 

 ing the hypodermic cells becoming cont&uous with the sense cells {se.). The 



