356 THE ANIMAL KINGDOM. 



part of the allantois (infra}. The urinary bladder so called of Teleostei and 

 Ganoidei is a dilatation or outgrowth of the urinary ducts themselves. 



The sexes are distinct in Vertebrata. Hermaphroditism may occur as 

 an abnormality, as a rule only in one Anuran and two Teleosteans. The 

 testis and ovary are alike derived from a thickened ridge of coelomic 

 epithelial cells. They are as a rule retained in the coelome, but in many 

 Mammalia the testes shift their position either temporarily or permanently 

 and are lodged in a pouch or caecum of the body wall which includes them 

 and a portion of the coelome, and is known as scrotum. The sperm is shed 

 into the coelome in Cyclostomi, in Dipnoi (?) and perhaps some Ganoidei : 

 but as a rule it is transported to the exterior by a network of tubes derived 

 from and in connection with the anterior region of the mesonephros and 

 thence through the Wolffian duct. This region of the mesonephros persists 

 in the Amniota and forms the coni vasculosi and vasa recta, while the 

 Wolffian duct becomes epididymis and vas deferens. Remnants of the 

 Wolffian duct are sometimes found in female Amniota (tube of ep- 

 oophoron ; duct of Gartner in Mammalia}. The ova are typically shed 

 into the coelome and are thence transported outwards by the Miillerian 

 duct, which is known as Fallopian tube or oviduct. It has a wide coelomic 

 aperture, and its walls for part of its course may become richly glandular, 

 secreting albumen and sometimes an egg-shell, whilst its lower section may 

 be dilated and as uterus x retain the ovum while it undergoes development. 

 Remnants of the Miillerian duct may be present in the male (hydatid of 

 Morgagni : uterus masculinus, p. 30, ante, of Mammalia], but it is only in 

 one Toad, Alytes, that it is connected directly to the testis and acts as vas 

 deferens. It may so act in Dipnoi and some Ganoidei, but in this case it 

 is not connected to the testis. In the male Gymnophiona and Bufo it 

 persists and has a glandular function. Exceptions to the typical condition 

 are (i) Cyclostomi and the Eels (Muraenidae), where sperm and ova are 

 conducted outwards by an abdominal pore or pores (infra) as are the ova 

 in a few Teleostei, e. g. Salmon : (2) Lepidosteus among Ganoidei and the 

 Teleostei, where there are genital ducts continuous with the glands (see 

 p. 89). Copulatory organs are formed as processes of the pelvic fins in 

 Elasmobranchii and Holocephali ; as organs varying in character attached 

 to the cloaca in Amniota. In male Mammalia, except Prototheria, the 

 organ is traversed by a continuous genito-urinary canal ; similar but rudi- 

 mentary organs are found in the female, and in some female Mammalia the 

 clitoris (homologue of the penis) is traversed by the urinary canal (p. 36, 

 ante). Accessory glands or diverticula are formed in connection with the 

 male genito-urinary duct in most Mammalia, some of which have corre- 

 sponding structures in the female. 



1 This name is also generally given to the lower section of the oviduct in Aves, &c. 



