Physiology of Hsematopinus tenuirostris, Burin. 97 



the rest of the chorion, only takes place outside the maternal 

 organism, when the embryo is so far developed that it will 

 soon quit the egg-capsule. Upon the operculum arise some 

 small hemispherical cells, from sixteen to eighteen in number, 

 which form the micropylar apparatus. They occur only on 

 the middle part of the operculum ; so that a broad margin 

 remains which shows exactly the same superficial structure as 

 the rest of the chorion. Between the micropylar cells the 

 surface of the operculum is uneven and finely granular. In 

 the middle of each cell of the micropylar apparatus *we see a 

 round aperture, the true micropyle. Round this, at some 

 little distance, runs a circular elevation, towards which radia- 

 ting grooves run from the orifice. From the true micropyle a 

 tine canal passes through the chorion into the cavity of the 

 egg. The micropylar apparatus is only developed on the 

 ovum after all the previously described structures have been 

 produced. It seems to me that the small rounded cells placed 

 above the vitelligenous cells (fig. 11, m) take part in its for- 

 mation. The vitelline membrane is separated from the 

 chorion throughout its whole extent, except at the periphery 

 of the operculum, where the two are firmly united. It has 

 only a temporary existence, and disappears during the deve- 

 lopment of the embryo. At the posterior pole of the egg — 

 that is, at the end which lies nearest to the uterus, there is a 

 peculiar structure, which was also found by Leuckart in the 

 eggs oiPediculm capitis, and by Landois in those of Phthirius 

 inguinalis. The latter describes it characteristically as a 

 " conical organ which appears as if composed of a tuft of 

 very fine aciculi, springing from a rather dark round space, 

 much like the individual florets in the flower of a composite 

 plant." Whether Leuckart's supposition that this structure 

 is an apprratus of attachment is correct must remain unde- 

 cided. It is certain, however, that this apparatus is connected 

 with the vitelline membrane, which becomes contracted below 

 into a fine tube, which 1 could trace distinctly to the structure 



now under consideration. 



The ovarian tubes are connected with the uterus by the 

 tubce. These are slender thin-walled tubes filled with a yel- 

 lowish cell-mass. The uterus is bicornute (uterus bicornis) ; 

 that is to say, it presents two nearly globular diverticula. 

 These open below into the upper broad part of the vagina. 

 Both uterus and vagina have an outer tolerably firm textureless 

 membrane and dark granular contents. The vagina, which is 

 surrounded by a network of fine circular and longitudinal 

 muscles, receives the two cement-glands before it opens into 

 the cloaca. These are lobulate bodies with an external en- 



