Prof. H. Karsten on llhynchoprion penetrans. 309 



penetrate through the epidermis, upon which it must first of all 

 get (which can hardly be regarded as probable); or else we must 

 assume (as indeed is done by the majority of writers on this 

 subject) that several larva? are developed simultaneously in the 

 ovary, and that these then break through the integuments of 

 the mother and thus reach the inner parts of the skin. The 

 anatomical characters above described do not accord with this 

 assumption of viviparity. 



The external sexual organs of the female consist of the cleft 

 terminal abdominal segment, forming apparently two pairs, 

 which preserve their form unchanged during the parasitic life 

 of the animal, and surround the cloaca, which lies parallel to 

 the surface of the skin, standing perpendicularly upwards. 



In the male also (PL IX. figs. 1, 2, & 9) the last segments 

 of the body are cleft, and of very peculiar form. Even in the 

 still undivided seventh half-segment, the ventral lamina, which 

 in general is somewhat less than the dorsal, is considerably 

 smaller and almost canaliform (figs. 1, 2, & 6). Then follow 

 two pairs of valvular or scale-like organs (fig. 6 a, b), each of 

 which should probably be regarded as a cleft and metamorphosed 

 dorsal or ventral plate. These laminae serve as the coverings of 

 the external organs of the generative apparatus (fig. 6 ; fig. 5, 

 seen from above). Beneath the upper external valve {a) on each 

 side a long-stalked forceps-like organ (k) is concealed, which 

 evidently serves the male as an organ of support and adhesion 

 during copulation. The branches of the forceps are shovel- 

 shaped ; the lower one moves upon the upper one by a broad 

 two-armed hinge, and both are fringed round the anterior mar- 

 gin with long stiff bristles. The inferior pair of valves (b), 

 which are longer than the upper, and clothed with short bristly 

 hairs, cover the base of two long tubuliform channeled organs 

 (x), open above throughout nearly their whole length. These 

 have their inner margin recurved inwardly and notched, and by 

 means of this are connected with another, central channeled organ 

 (z) open beneath, — the lateral walls of this organ, which are like- 

 wise recurved inwardly at the middle part, being interlocked with 

 them, whilst posteriorly they are rolled inwards and form two 

 tubes for the reception of the two seminal canals (v). Two long 

 narrow laminae (y), with the upper margin undivided and the 

 lower one emarginate in the middle, conceal this organ from 

 above. During copulation, these laminse bend downwards almost 

 at a right angle from their narrow middle part (e), and thus 

 no doubt serve to attach the two individuals to each other. The 

 central channel (z), which is open below, has, on the lower sur- 

 face of its decurved apex, a fine orifice, which evidently serves 

 for the passage of the extremity of the long, round, filiform, but 



