

106 M. O. Strobelt on the Anatomy and ' 



the latter contract ; at the same time the muscles aa and bb 

 also contract. By this means the upper part of the vagina is 

 shortened and the lower part dilated, and the egg is pressed 

 through the abbreviated vagina into its lower dilated extre- 

 mity. The circular muscles (c) now come into action, and 

 force the egg lower down ; the muscles cc contract and enlarge 

 the genital cleft, and the egg is completely pressed out of the 

 genital aperture. 



The muscular apparatus of the male sexual organs is much 

 more simple, as indeed lies in the nature of the case. Here 

 we have only two muscles, which originate in the last abdo- 

 minal segment, and are inserted at the base of the penis. One 

 of them serves to push it forth, the other to retract it after 

 protrusion. 



Anatomy and Physiology of the Respiratory Organs. 



The respiratory organs of Hematopinus tenuirostris consist, 

 as in all insects, of stigmata and tracheae. Seven pairs of 

 stigmata are present. These are placed, as in most Pedicu- 

 lina, somewhat towards the ventral side, and always sym- 

 metrically on the two sides of the segments, whereas in other 

 insects they are for the most part situated towards the back. 

 They advance to the middle of the segments, which is also 

 the case in the Pulicidse and Acanthiadag. In the other 

 Hexapods, on the contrary, we generally find them between 

 two segments. The first pair is in the thorax at the ba^e of 

 the second pair of legs, and therefore in the mesothorax. This 

 appears to be the case throughout the genus Hcematopinus, in 

 contradistinction to Pediculus and Plithirius, in which the 

 thoracic stigmata belong to the pro thorax. The remaining 

 six pairs are situated in the abdominal segments from the 

 second to the seventh. Besides its size the thoracic stigma is 

 distinguished by its form from the abdominal stigmata. The 

 latter resemble a closed flower-bud (fig. 3), whereas the former 

 rather resembles an open flower. The different stigmata have 

 a small circular aperture surrounded by a chitinous ring 

 (fig. 3, b). Parallel to the latter, three other chitinous rings 

 surround the globular stigma. The space between the first 

 ring placed immediately round the aperture and the second, 

 and in the stigmata of the thorax that also between the 

 second and third, are divided into regular areas by radiating 

 grooves. In the bottom of the stigmata, opposite to the ex- 

 ternal aperture, we observe a number of fine hairs directed 

 outwards. These serve to prevent the entrance of foreign 



_ -•* ■ ft ^ m w * 



bod 



tunica adventitia (fig. 3, d) 



