428 THE ANIMAL KINGDOM. 



PhysostomL In the latter they are conveyed outwards by the abdominal 

 pore or pores ; in Ganoidei by the supposed Mullerian ducts ; in the other 

 three orders by Mullerian ducts or oviducts proper. These have in Elas- 

 mobranchii a common internal median aperture, a narrow ciliated duct, a 

 nidamental gland which secretes a shell and the albumen of the egg, and is 

 largest in the oviparous genera, and a dilated posterior part or uterus, in 

 which the ova develope in viviparous species. The oviducts are convoluted 

 in Dipnoi, and their walls glandular. In Ceratodus the ova are laid in 

 strings imbedded in albumen. The ovaries of the Muraenidae are plate- 

 like bands ; of Salmonidae lamellate ; in other Teleostei saccular, the ova 

 being produced by a small lateral streak on one wall, e. g. Ophrydium 

 barbatum, by processes of the wall, e. g. Lophobranchii or by lamellae trans- 

 verse, e. g. Clupea harengus, or longitudinal, e. g. Zeus faber. The sticky 

 coat of the ova appears to be formed from the follicle cells. 



The testis is saccular only in the Teleostean Syngnathus acus ; it is 

 composed in all other Fish of tubuli seminiferi. The sperm is conveyed by 

 vasa efferentia to the mesonephros in Elasmobranchii, Holocephali, chon- 

 drostean Ganoidei and Lepidosteus. It appears to be shed into the coelome 

 in Dipnoi, and is thence conveyed away either by the abdominal pores or 

 by Mullerian ducts, which are present ; the latter may be the case with 

 Polypterus and Amia, as it was once supposed to be with other Ganoids. 

 The ducts in Teleostei are continuous with the gland, as in the female, 

 except in Muraenidae, where, though they are present, the sperm is shed 

 into the coelome, whence it is conveyed away by the single abdominal 

 pore. The ducts are often dilated terminally, or furnished with vesiculae 

 seminales. The Mullerian ducts open in Elasmobranchii and Dipnoi into 

 the cloaca dorsally to the rectum ; in Holocephali externally between the 

 anus and urinary apertures. For Ganoidei and Teleostei, see p. 427. 



Copulatory organs (= pterygopodia) are developed in connection with 

 the metapterygium of the hind-limb in Elasmobranchii and Holocephali. A 

 cartilaginous skeleton supports a deep groove, into which opens a saccular 

 gland- in Sharks and Holocephali, a compound tubular gland in Rays. 

 Sperm has been found in the sac in some Sharks and the Holocephali. 

 Dilator and flexor muscles are connected with the apparatus. Impreg- 

 nation is internal, as it must be in viviparous Teleostei (infra}. The sperm 

 ' milt ' in other Fish is shed over the ova after they are laid. 



The majority of Sharks (except e. g. Scyllidae, Scylliolamnidae, Ces- 

 tracion) and the Torpedo among the Rays, certain Teleostei (many Blen- 

 nidae and Cyprinodontidae] are viviparous. The Teleosteans in question 

 retain the ova in the ovary, the Elasmobranchii in the uterine portion of 

 the oviduct ; and in some instances (Mustelus laevis, Carcharias glaucus) the 

 yolk-sac is thrown into folds, which fit into corresponding depressions of 

 the vascular uterine walls, forming a kind of placenta. Among Teleostei 



