The ejaculatory duct which opens on the ninth abdominal sternum in the adult male arises in the tenth abdominal embryonic segment and subsequently moves forward.
In the anterior part of the gland are seen bundles of striped muscle fibres, which are of interest when the comparative ana Ampulla of vas deferens tomy of the gland Cut end of great sacrois studied: they are 1 sciatic ligament Common ejaculatory duct Levator ani than in old prostates.
The median vagina, spermatheca and ejaculatory duct are, on the other hand, formed by ectodermal inpushings.
Where the vesiculae join the ampullae of the vasa deferentia the ejaculatory ducts are formed; these are narrow and thin-walled, and run, side by side, through the prostate to open into the floor of the prostatic urethra.
On the other hand, the ejaculatory duct with its verticillate sac in the male of Cypris and other genera is a feature scarcely less remarkable.
Close to the opening of the utriculus the ejaculatory ducts, already mentioned, open into the urethra by very small apertures.
The independent opening of the genital ducts and the absence of an ectodermal vagina and ejaculatory duct are remarkable archaic features of these insects, as has been pointed out by J.