554 On a new Cyprinodont Fish from Jolwre. 



skeletal support for the priapium ; it tapers anteriorly and 

 extends on the proctal side nearly to the anterior end. A 

 nid-ventral rod of bone runs the whole length of the pri- 

 apium ; the toxactinium articulates with its anterior end, the 

 ctenactinium with its posterior end ; it seems probable that 

 these are modified pelvic fin-rays and that the bony rod with 

 which they articulate is thepelvis. The last-named lies between 

 a pair of longitudinal muscles which also run the whole length 

 of the organ and are more or less symmetrically arranged 

 except in the region of the anus, where they send out a dorsal 

 branch that runs on the aproctal side of the priapium right 

 up into the body and is attached high up on the inner side 

 of the cleithrum of the proctal side. The anal and urinary 

 openings and in front of them the prolongation of thecleithra 

 mentioned above lie directly above these ventral muscles. 

 A pair of dorsal muscles also run the whole length of the 

 priapium, lying nearly symmetrically and directly above 

 the ventral muscles except in two regions : (1) the region of 

 the anus, where the cleithral process and the intestine separate 

 them from the ventral muscles and with the cleithral branch 

 of the latter displace them towards the proctal side ; (2) the 

 region of the terminal coil of the vas deferens ; here the 

 dorsal muscles unite, taper, and are confined to the aproctal 

 side. 



The pectoral muscles attached to the expanded hypo- 

 coracoids are continued forward into the dorsal part of the 

 priapium, tapering anteriorly and ending above the base of 

 the toxactinium. 



It is evident that the priapium is an intromittent organ. 

 Probably its distal end is brought close against or just within 

 the genital aperture of the female, and the ctenactinium is 

 used to hold it in position ; the toxactinium may also assist 

 in this ; the dorsal and ventral longitudinal muscles of the 

 priapium are probably concerned chiefly with the movement 

 of these two bony appendages. Contraction of the cleithral 

 branch of the ventral priapial muscles would doubtless bring 

 the distal part of the organ nearer the body, whilst the reverse 

 effect would be produced by contraction of the pectoral 

 muscles that pass into it anteriorly. The great length of the 

 vas deferens may be due to the need for the plentiful supply 

 of a glandular secretion in which the spermatozoa may live. 



It is very remarkable that this little fish should have 

 developed so complex an organ for the purpose of internal 

 fertilization. The whole structure of the priapium is quite 

 unlike that of any other copulatory organ known among fishes, 

 and I believe that the coiling of the vas deferens to form a 



