310 Prof. H. Karsten on Rhynchoprion penetrans. 



tubular penis (p), which has its apex bent downwards. I found 

 this organ once protruded from the rest of the generative appa- 

 ratus in the manner shown in fig. 6, in a male engaged in the 

 act of copulation ; in another individual, in which it was likewise 

 protruded, I found the apex broken off. This central channeled 

 organ (fig. 6 z), which immediately encloses the penis, is en- 

 gaged at its base in another channel open beneath, enclosed in 

 the abdominal cavity of the animal, and the lateral walls of 

 which are dilated anteriorly into broad, nearly rhombic lamina? 

 (p), which can be drawn towards the anterior walls of the abdo- 

 minal cavity by means of broad muscles (m). 



In the bottom of this channel, turned towards the back of 

 the animal, and between these two plates, is attached the long, 

 slender, linear stem of a stirrup-shaped or two-armed and almost 

 sledge-shaped body (s), directed towards the lower and anterior 

 region of the body, upon which a muscle, attached to the poste- 

 rior extremity of the abdominal cavity, is inserted. By means 

 of these two muscles the entire sexual apparatus can be pro- 

 truded and retracted. 



The margins of the slender stem-like part (fig. 6 c) of this 

 channeled chitinous organ are bent upwards, and thus again 

 form on the inferiorly open channel a narrower channel open 

 above on each side, in which the two multifariously twisted se- 

 minal cords (tigs. 5 & 6 v) probably lie ; these convey the long 

 filiform spermatozoids produced in the testis {g) into the central 

 channeled organ (z) in which the penis is concealed. 



When the sexual apparatus is retracted, the canal of the semi- 

 nal cords (c) forms with the sheath of the penis {z) an angle of 

 45°, turned upwards ; the laminar extremity is situated in that 

 region of the abdomen which is covered by the wing-plates. 

 (It is shown through the integument in PI. IX. fig. 1.) In 

 fig. 6, to save room, it is shown in an oblique position, although 

 truly, in the protruded condition of the external generative organs 

 here delineated, the organs c and x form a still more obtuse 

 angle. 



From the form of the male sexual apparatus it follows that in 

 copulation the female is not borne by the male, as in Pulex irri~ 

 tans, but that the female carries the male. 



Besides this peculiarity, the different formation of the respi- 

 ratory organs consequent on the parasitic mode of life, the 

 different form of the maxillae, and also the form of the palpiform 

 appendages of the cleft labium are the chief characters which 

 warrant the separation of this insect from the genus Pulex, as 

 the type of a peculiar generic group. The labium of Pulex is 

 indeed equally deeply cleft; but its sections are not jointed as in 

 our animal, but only pseudo-articulated by the chitinization of 



