146 CALIFORNIA ACADEMY OF SCIENCES. 



principal anatomical characters are tabulated, and a 

 long description of the mouth-parts given. The latter, 

 however, is almost entirelv incorrect. The mouth- 

 parts were described wrongly at first by Nitzsch, then 

 by Kramer, and finally by Rudow. Their correct expla- 

 nation is due to Grosse. Rudow's paper contains an 

 important statement concerning the number of egg- 

 tubules in Amblijceran females. He says that there are 

 five present of which two are rudimentary. Nitzsch 

 could find but three, and Grosse apparently made no 

 determination of the number present. In 1869, also, 

 Melnikow published in Archiv fiir Naturgeschichte, 

 vol. XXXV, an embryological paper, " Beitrage zur 

 Embryonal-entwicklung der Insekten" in which the 

 embryology of the Mallophaga is described. Nusbaum 

 in his paper, "Zur Entwicklungsgeschichte der Aus- 

 fiihrungsgange der Sexualdriisen bei den Insekten," 

 in Zoologischer Anzeiger for 1882, describes mainly two 

 Mallophagan species, Lipeurus bacillus and Goniocotes 

 hologaster. 



I . General External Anatomy. 



External Form and Body-ivall. — The body is gener- 

 ally very much flattened dorsoventrally. The segments 

 of the thorax are often apparently only two, the meso- 

 notum and metanotum being united. In others, how- 

 ever, the two are distinct although the former is nar- 

 row. In longitudinal sections of Menopon titan (plate 

 x, fig. 1), the mesonotum (To) is seen to be sep- 

 arated from the metanotum (T3) by a non-chitinized 

 space, and is depressed below the level of the latter. 

 The number of abdominal segments varies, but the 

 largest is ten. The number in some cases varies with 

 the sex. The head is flat, horizontal, situated closely 



