740 THE GENERATIVE ORGANS. 
sternum in front and with the sides of the penis internally. 
They are undoubtedly the homologues of the great claspers of 
the male Hymenoptera, and of the so-called external sheath of 
the penis. Their position immediately behind the progenital 
sternum shows that they are the lateral appendages of the 
progenital or mesogenital somite, and their developmental 
history, as well as the position of the claspers in the Hymen- 
optera, renders it almost certain that they are appendages of 
the progenital somite. 
In this case they clearly correspond with the inferior blades 
of the ovipositor in Locusta viridissima. 
The Penis in the Muscide is a very complex organ. It con- 
sists of a membranous, papilla-like projection from the thin 
Fic. 105.—A transverse section of the penis of a Blow-fly. 4, hypophallus ; 
Pp, paraphallus. 
integument of the roof of the genital sinus, at the extremity of 
which the ejaculatory duct opens externally. 
This membranous papilla contains a large blood sinus and is 
capable of erection; it is supported and protected by a com- 
plex chitinous framework, which consists of a pair of para- 
phalli enclosing its base, and of a large, curved, ventral plate, 
which I shall term the hypophallus. 
DESCRIPTION OF PLATE LIT. 
View of the penis from its under surface ; 4, bulb; g, anterior gonapophyses ; 1, 
hypophallus ; /, paraphallus ; 9, orifice of ejaculatory duct ; 7, ridges of epipleura. 
