746 THE GENERATIVE ORGANS. 
syndesmoses, so as to allow of the complete invagination of 
the ovipositor when at rest. 
The second annulus corresponds with the seventh abdominal 
somite. Its dorsal plate is narrow, suddenly broadening near 
its posterior extremity ; it has no spiracle. Its ventral plate 
is also very narrow, and is shorter than the dorsal plate. 
The third segment of the ovipositor is the progenital. It 
exhibits two narrow dorsal plates, one on either side of the 
median line. These articulate behind with the anal segment. 
Fic. 108.—A, Dorsal view of the plates of the anal somite of a female Blow-fly. 
a, anal scale; d, dorsal plate; @, apodeme of the sternal plate. B, The 
ventral plate of the anal segment. C, A transverse section through the 
extremity of the ovipositor. d, dorsal plate of the anal somite; a, scales ; 
5, sternal plate ; s/, sternal plate of the eighth abdominal somite. 
Its ventral plate is very narrow, but terminates behind in two 
cornua, which form the ventral edge of the sexual opening. 
The terminal, or anal somite, consists of four sclerites, 
which surround the anus. These are a triangular dorsal plate, 
which in form resembles the telson of a Crustacean (Figs. 107, 
108, d), a scoop-shaped ventral plate with two long apodemes 
(Fig. 108, B), and a pair of scales, which articulate with 
the dorsal plates of the progenital somites, and the dorsal 
and ventral plate of the anal somite (Figs. 107, 108, a). It 
