THE ANATOMY OF POLYPTBEUS. 325 



however, are smaller as compared with the testis-duct in the young than in the adult. 

 It is noteworthy also that the vas deferens, which in the young is very thick-walled and 

 has a larger lumen, is much larger as compared with the ureter in the young than in 

 the mature individual (PI. LI. figs. 11, 18, v.d.). 



In the young Polyptervs the duct of the testis runs forward a short distance 

 anteriorly to the testis. This portion of the duct could not be traced with certainty in 

 the adult. No opening in the young male was found, however, into the body-cavity. 



In the very young male, 9 cm. in length, the tubules of the testis are foreshadowed 

 by the nuclei being arranged in double rows, but there are no lumina; the duct, 

 however, has a wide lumen and is well formed (PL LII. fig. 19, t.d.). At this stage the 

 tubules of the testis-ridge are not yet developed ; the duct, however, is here well formed, 

 as opposite the testis. Posteriorly the vasa deferentia end blindly in the wall of the 

 ureter (PI. LII. fig. 20, w.v.u.). 



III. The Female Organs. 



The following observations have been made on adult female specimens of 

 P. senegalus and P. lapradei taken at all times of the year, and also upon specimens 

 of the young female P. senegalus 9 cm. in length. 



The funnel-like opening of the oviducts into the body-cavity (PI. L. fig. 1, p.ap.od.) 

 were mentioned and figured by Joh. Miiller ; the ducts were figured in more detail by 

 Hyrtl, and the ovaries were described. My own observations, however, do not in some 

 respects agree with those of the latter author. According to Hyrtl the two oviducts 

 unite to form a urinogenital sinus, into which the two ureters open by a common mid- 

 dorsal aperture. 



I have carefully studied the adults of both species found in the Gambia, and I find 

 that the ureters are dilated posteriorly, lying closely approximated to each other, but 

 not communicating, except immediately before opening to the exterior (PL L. figs. 1, 

 4, u. ; fig. 4, s.u.g.s.). Shortly before the ureters open to the exterior the oviducts open 

 into their lateral walls precisely as do the vasa deferentia in the male (PL L. fig. 4, g.ap.). 

 Further, in the young female 9 cm. in length the course of these ducts has exactly the 

 same relation to the ureter as in the male, only that the oviducts are considerably more 

 dilated ; they lie immediately over the genital ridge, which anteriorly is developed 

 into the ovary (PL LII. figs. 21, 22, 23, mes.o.). 



The great difference between the sets of organs in the male and female is that in 

 the male the genital gland discharges directly into the duct, whereas in the female 

 the genital products are shed free into the body-cavity, and thence find their way to 

 the mouth of the duct. Were the outer wall of the duct in the female carried 

 forwards to enclose that side of the ovary from which the ova are shed, or were the 

 testis-duct in the male open anteriorly to receive the products of the testis from the 

 body-cavity, the arrangement would be precisely analogous in the male and female. 



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