ON THE OVIPAROUS SPECIES OF ONYCHOPHORA. 371 



Crural glands are apparently developed in the male only, 

 and their apertures are more or less conspicuous on the under 

 surfaces of more or fewer of the legs in all three species 

 (fig-. 28). They are present in most if not all of the legs, and 

 I include under this name the glands of the last pair of legs, 

 whose apertures lie at either side of the genital orifice. The 

 apertures of the crural glands are borne on white papillae 

 which are retractile, and may be considerably protruded in 

 the form of thin-walled vesicles. Behind the male orifice is 

 yet another pair of white papillae, probably bearing the 

 apertures of accessory glands. 



Tracheal pits occur scattered over the surface of the 

 body, as seen in sections of P. oviparus (fig. 5, Tr. P.). In 

 this species (and probably in the others) there is a tracheal 

 pit immediately in front of the mouth, and a pair of very 

 large ones opening in the buccal cavity just behind and close 

 to the base of the inner jaw on each side, and running back- 

 wards for some distance, at first just outside the lateral nerve- 

 cords (fig. 5, B. Tr.) and then above them and just inside the 

 salivary glands. These buccal tracheal pits have a thick 

 chitinous lining, and may be traced back in a series of 

 transverse sections very nearly to the level of the second, 

 pair of walking legs. They give off along their course and 

 from their extremities an immense number of very fine 

 tracheal tubes. When the jaws are removed, these enor- 

 mously elongated tracheal pits may be pulled out in connec- 

 tion with them, and the chitinous lining of the pit appears to 

 pass over into the chitinous covering of the smallest accessory 

 tooth of the inner jaw. 



Integument. — The structure of the integument closely 

 resembles that described by Gaffron (1) for P. Edwardsii. 

 As usual, it is furrowed by narrow transverse grooves^ and 

 produced into papilhe of varying size on the intervening- 

 ridges. There is approximately a single row of papilhe on 

 each ridge. The pigment is lodged in the polygonal, 

 nucleated, epidermic cells, outside each of which the cuticle 

 forms a small, transparent, sharp-pointed, scale-like spine. 



