22 MR. C. TATE REGAN OX THE 



8, Use of the Friapium. 



In oviparous Oypriuodonts [Fmidulus and Cyjjrinodon), New- 

 man (5) has observed tJie intercourse of the sexes ; the male and 

 female lie side by side and looking in the same direction, and the 

 male clasps his mate by folding his dorsal and anal fins across 

 her, whilst the paired fins also may interlock ; in this way the 

 eggs and sperm are extruded in such close proximity that fertili- 

 zation is assured. 



It seems likely that in the Phallostethinfe also the male and 

 female take up a similar position, the female lying on the- 

 aproctal side of her mate. 



In Phallostethus the toxactinium, which curves towards the 

 aproctal side, may grip her under the chin or even be held in 

 her mouth, whilst the serrated edge of the ctenactinium may 

 give it a firm hold on the pectoral region in front of and on the 

 far side of the genital orifice, in order that the seminal papilla 

 may be placed against or introduced into the latter. 



In Neostethus in seems likely that during intercourse the female 

 may be held by the ctenactinium aci^oss the back of the head, the 

 anterior descending part lying on her distal side and the terminal 

 part that at rest curves across under the chin of the male now 

 curving towards him, perhaps under hers. The spinous process. 

 of the ctenactinium and the pialvinular spine would stick into 

 her on the side near the male. The posterior end of the priapium 

 may be held in the depression into which the oviduct opens, whilst 

 the tei-minal projecting part of the fold that roofs the efferent 

 groove and the membranous fringe below it may form a sort of 

 tube for insertion into the genital apertiu-e of the female. 



The asymmetry of the postanal papilla? of the female may be 

 due to the side by side position presumablj^ adopted ; if so, it 

 may be supposed that a male with the right side aproctal would 

 pair with a female that had the smaller papilla on the left side,, 

 and vice vei'sd. 



It is possible that no part of the priapium is actually intro- 

 duced into the oviduct, and that the spermatophores, first 

 discharged into the glandular groove and then ejected through 

 the efferent groove, may adhere to the surface of the postanal 

 papillae and of the depression into which the oviduct opens, and 

 that they may be introduced into the oviduct by the action of 

 the papillfe. 



The infrasulcar prominence may prevent the flow of the 

 seminal fluid outwards or forwards at the place where it exerts 

 the greatest pressure, and the pulvinular appendage may possibly 

 help to drive the glandular secretion backwards. 



In both Phallostethus and JS^eostethus the probable effect of the 

 contraction of the longitudinal muscles of the aproctal side and 

 of the pleuro-pria.pial muscle would be to move the posterior end 

 of the priapium aproctally ; an additional effect in Iieostethu» 

 would be to close the glandular groove. 



