110 Mr. F. Balfour-Biowne on the 



protected by an elongated, more or less pointed, cliitinous 

 "tongue'^ (b), which lies forward along the side of the main 

 lobe and in a groove {b') specially shaped for it. On the 

 outer face of this '^ tongue " is a groove {g), which com- 

 mences sometimes near the apex and sometimes about halfway 

 back, according to the species, and extends backward beyond 

 the base of the tongue and down the dorsal aspect of the 

 a?deagus to its base (g'} . 



On the side of this tongue or immediately posterior to it is 

 a curious mass of material {d), which in several species partly 

 bulges outwards to form a small " wing " (d'). This pale- 

 coloured material is apparently an expansible sac and is 

 easily distinguished from the dark surrounding chitin. I 

 imagine that it is in the wall of the ductus, and capable of 

 being bulged outwards, perhaps in the passage of the sperma- 

 tophore (4). The groove already referred to, on the outside of 

 the tongue, passes immediately dorsal to this saccular region. 



On the right side of the asdeagus there is in some species 

 a thin membrane which I have called the " hood " (c). It 

 aiises some way behind the apex of the main lobe, and varies 

 considerably in extent. Sometimes it reaches nearly to the 

 base of the jedeagus, and stands up merely as a flat mem- 

 branous structure (e. g., H. riijicol/is, heydeni), and in one 

 case {H. immaculatus) it folds right over the convexity of the 

 redeagus, so as to shut in a considerable portion of the right 

 side of it. In some cases this hood is reduced to a minute 

 lobe (e. g., H. nomax), and in others it is entirely absent. 



I have mentioned that Sharp's figure of the aideagus of 

 //./tJtJtis represents one of the simpler types, and we can 

 trace various stages in complexity in the different species. 

 The simplest types have no " hood" and no " saccular region," 

 e. g., U. apicalis and jiuviatilis. H. nomax has the merest 

 trace of a hood, but possesses an elaborate saccular membrane. 

 H. loehnckei has a larger and quite distinct hood and a well- 

 marked saccular membrane. H. ruJicoUis and heydeni have 

 both structures better developed, and H. immaculatus has a 

 well-marked saccular region and the highest development of 

 hood. 



The male armature of Haliplus is built upon exactly the 

 same general lines as that of Dytiscus, which has been 

 described by various authors. Berlese (3, p. 320) calls the 

 main lobe the '' hypophallus" and the tongue the "epi- 

 phallus." Blunck (4) speaks of them as the "penis'' and 

 covering-piece ('^ Deckapparat "), while Sharp (19) calls 

 them " median lobe " and " membranous tongue." In 

 Dytibcus, however, the whole armature is fairly symmetrical, 



