THB MALE GENEBATIVE OBOANS. 105 



plate which seems to coalesce laterally with the seventh, at least on the 

 right side. The seventh and eighth are each very broad and strong, and 

 are minutely tuberculated or shagreened on their surface. The eighth 

 is deeply notched behind, the edges of the notch being produced laterally 

 to form the external pair of valve-like pieces already mentioned. The 

 internal pair of valve-like pieces are quite distinct from this plate, and 

 surround the extremity of the rectum which opens between them ; they are 

 united with the notch by a thin membrane. I believe they form part of 

 the ninth segment. 



The junction of the sixth and seventh segments on the right side is very 

 considerably thickened, and supports, or more correctly these segments 

 are supported, by a broad process which becomes gradually narrower, and 

 curving round their ventral aspect forms a strong chitinous loop ; a very 

 rudimentary process exists on the left side, but never joins this loop. 

 Numerous muscular bands are inserted into the edge of the loop, and a 

 strong muscle is attached to its thick extremity. The loop forms a hinge 

 upon which the four posterior segments move. It is united loosely by 

 membrane to the ventral plate of the fifth and to the ventral plate of 

 the eighth segment. The membrane between it and the eighth segment 

 forms a pouch, which contains the male organ when the segments 

 are retracted ; the loop then lies along the inner margin of the notch in 

 the fifth abdominal ventral plate (Plate DL, fig 6 represents the position 

 of the loop both during the exsertion and retraction of the four posterior 

 segments). 



The eighth segment is continuous with the outer valve-like appendages 

 (Plate IX., figs. 8 & 9), which are curved and covered upon their 

 outer surface with hairs directed forwards ; they probably embrace 

 the ovipositor during copulation.* Externally each is prolonged for- 

 ward as a slender but strong-curved rod, which unites it with a heart- 

 shaped ventral plate. The rods lie along the lateral margins of the genital 

 fissure (Plate IX., fig. 9), and the ventral plate with which they are 

 united, lies within its anterior border ; it ia united by the membranous 

 pouch with the loop. 



The posterior prolongations of the dorsal plate are probably not to be 



* I have never been able to observe the sexual act in the blow-fly. 

 When kept in captivity I have never known them either to perfect ova or 

 spermatozoa, neither have I been able to hear of anyone having observed 

 the act. By comparing the organs carefully, I have attained the results 

 which I have set down as the probable relations and uses of the various 

 parts concerned. 



