612 Mr. D. Sharp and Mr. F. Muir on the Comparative 



keep open certain spaces between the sac and the wall of 

 the female tubes. Observations on the positions taken up 

 by the sacs within the vagina during copulation are greatly 

 to be desired. 



The pressure necessary to drive the viscid fluid from the 

 testes through the long slender ducts must be very 

 great, and the thick coating of muscles surrounding the 

 ducts serves to this end. The pressure behind such a 

 flagellum as is found in Baryrhynchns miles, where it is 

 12 mm. long, and "006 mm. in outside diameter toward the 

 tips, must be well directed and considerable. 



It is worthy of note that the armature of the sac of 

 Donacia sericea, etc., recalls the parts of the aedeagus, 

 there being a median lobe, through which the ejaculatory 

 duct passes, and opens on its apex, and a pair of lateral 

 lobes. There is, as it were, a secondary aedeagus within 

 the aedeagus. To find out the action of these pieces 

 during copulation would be of interest. 



Whether the lateral lobes in such a trilobe form as 

 Ceratognathus pass into the vagina and then diverge and 

 thus hold the female, we are unable to say. In Stenus 

 speculator (fig. 232) the lateral lobes are placed along the 

 outside and hold the female. In Coccinellidae they are 

 placed on the outside of the female venter, and appear 

 to have no hold. In some of the Cistelidae the hind 

 body-segment is developed into claspers to retain the 

 female. In Malthodes (fig. 233) and Malthimis (fig. 235) 

 the last abdominal segment is used as a clasper, and 

 the last segments of the females have depressions into 

 which the ends of the claspers fit to give them a firmer 

 hold. In Telcphorus and Ehagonycha the edge of the 

 vagina is held between the tongue of the tegmen (fig. 286a) 

 and the median lobe. In these species the aedeagus takes 

 nearly a half turn durit)g copulation (fig. 238). The 

 twisting of the aedeagus during copulation is common to 

 many forms, and in some it makes a complete half turn. 

 This is the case in the Caraboid type. In such an one as 

 Dytiscus punctulatus the aedeagus, when at rest and drawn 

 into the abdomen, lies on its side, and when thrust out the 

 median lobe curves downwards, but its true orientation is 

 with the median lobe curved upward as we figure it (fig. 37). 

 It is probable that in many forms the female does not 

 play an entirely passive part in the act of copulation ; as 

 to which see the remark made under Cyphon. 



