Physiology o/^H&matopinus tenuirostris, Barm. 89 



canal (fig. 12, d) in a circle. They are the six rectal gland* 

 of the animal. The whole intestinal canal is accompanied by 

 two strong tracheal stems, one on eacli side, the ramifications 

 of which go to the wall of the intestine, and run along the 

 grooves which exist between the rectal glands. 



As regards the accessory organs of the tr actus intestinalis, 

 the Malpighian vessels have first to be mentioned. These, 

 which are four in number, are inserted into the lower end of 

 the stomach, or into the upper end of the intestine (for no 

 definite boundary can be drawn between the two), and remain 

 isolated throughout their course. They are narrow (0*028 

 millim.), but attain the considerable length of 1 # 287 millim., 

 and present a hyaline structureless membrane and finely 

 granular pale yellow contents. 



We find two kinds of salivary glands in Hcematopinus 

 tenuirostris, elongated and globular, situated on both sides of 

 the upper wall of the stomach. Landois also describes two 

 pairs in Phtliirius inguinalis and Pediculits vestimenti, and 

 names them u bean-shaped " and " horseshoe-shaped " (23, 

 p. 9, and 24, p. 39). The former represent our globular, 

 and the latter our elongated glands. As regards the latter, 

 they always appear horseshoe-shaped in situ, and are 0*473 

 millim. long and 0'041 millim. broad. The efferent duct, 

 however, is not situated, as in Phtliirius inguinalis, at the 

 curvature of the horseshoe, but at the end of the gland, so that 

 the whole has the form of a thread thickened and bent back 

 at its upper end. The gland itself is enclosed by a clear 

 structureless membrane ; the dark yellow contents show no 

 differentiation. The efferent duct has also a structureless 

 envelope, which forms the continuation of the membrane of 

 the salivary gland ; its contents, however, are pale yellow and 

 but slightly granulated. The outer envelope of the globular 

 salivary glands is likewise structureless, as also the membrane 

 of their efferent ducts ; their contents, however, differ essen- 

 tially from those of the preceding in so far that they are of a 

 lighter colour and show distinct round cells. The diameter 

 of the glandular ball is about 0*090 millim. The efferent 

 ducts of both are throughout uniformly narrow (about 0*015 

 millim.), and attain a considerable length. Both pairs of 

 salivary glands are placed close to the upper margin of the 

 stomach, and from this point send forth their efferent ducts 

 parallel -to the oesophagus to the mouth. 



There remains to be mentioned an organ which was named 

 "liver" by Hooke, and "buik-klier" or " ventral salivary 

 gland " by Swammerdam, but to which Landois gives the 

 indifferent name of the u stomachal disk " ( u Magcnschiebe "). 



Ann. & Mag. N. Hist. Ser. 5. Vol. xi. 7 



