1900.] ANATOMY OF POLTPTEEUS. 431 



published of the anatomy of Pobjpterus are either deficient or in- 

 accurate. 



In the present paper, I have described in detail the uriuogenital 

 system of the male and female Pol/ypt&rus, together with the later 

 stages of the development of these organs. I have also added 

 observations upon the vascular system, the external gills, the 

 abdominal pores, the anal fin, and the skull. 



In obtaining my material, I was aided by a grant of <£50 from 

 the Balfour Fund of the University of Cambridge. The work has 

 been done in Mr. Adam Sedgwick's laboratory. To Mr. Sedgwick, 

 Mr. Graham Kerr, and Prof. Howes my thanks are due for much 

 help and advice. 



The Male Organs. — In the adult male Polypteras a ridge of 

 testicular tubules extends on either side the entire length of the 

 body, but is only functional towards the anterior end of the ridge, 

 where it swells out to form a conspicuous lobulated testis. A 

 longitudinal duct lies at the base of the whole ridge ventral to and 

 parallel with the ureter. Into this duct the tubules of the testis 

 and of the testis-ridge open by very numerous short ducts. 



The duct on either side leaves the testis-ridge as the " vas 

 deferens," and running backwards in the same sheath of connective 

 tissue as the ureter, opens upon a papilla into the uriuogenital 

 sinus just before the latter opens to the exterior. The spermatozoa 

 are very small, about the length of the long axis of a red blood- 

 corpuscle, slightly swollen anteriorly, tapering posteriorly. 



The duct of the testis-ridge is developed before the tubules of 

 either the testis or testis-ridge, but in a specimen 9 cm. in length 

 ends blindly in the wall of the ureter. 



The Female Organs. — The funnel-like openings of the oviduct 

 into the body-cavity were mentioned and figured by Joh. Miiller 

 and again by Hyrtl. 



According to Hyrtl, the two oviducts unite to form a uriuo- 

 genital sinus, into which the two ureters open by a common mid- 

 dorsal aperture. 



I find, however, that the ureters are dilated posteriorly, lying 

 closely approximated to one another, but not communicating except 

 immediately before opening to the exterior. Shortly before they 

 open to the exterior, the oviducts open into their lateral walls 

 precisely as do the vasa deferentia in the male. 



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 in the 

 female. The ducts at this stage, like those of the male, end 

 blindly in the lateral wall of the ureter. The peritoneal opening 

 of the oviduct is already open at this early stage. 



The ovary of Polypterus develops as a genital ridge lying on 

 either side along the ventral surface of the kidney, from which it 

 is separated posteriorly by the oviduct. The ovary becomes early 

 divided into numerous compartments, on the external walls of 

 which the ova are developed. 



29* 



