UROGENITAL SYSTEM. 



333 



mercy of the water, but a number of species (Embiotocids, Gambusia, several 

 Cyprinodonts, etc.) are viviparous, the development of the eggs taking place in the 

 ovary, which sometimes provides nourishment for the growing young. In the 

 lophobranchs the eggs are received in a pouch between the ventral fins of the male 

 and are incubated there. Other peculiar breeding habits are known. 



FIG. 332. Relations of oviducts and pori abdominales in Coregonus, after Weber, 

 a, anus; i, intestine; n, nephridial opening; o, ovary; p, pore of right side; r, opening of 

 oviduct. 



DIPNOI. In the dipnoi more normal conditions occur. There are oviducts 

 with inner ostia, resembling in structure, at least, the Miillerian ducts, and especially 

 those of the amphibia, like them secreting a gelatinous substance around the eggs. 

 These same ducts are also retained in the male Ceratodus and to a less extent in 

 the other genera (Lcpidosiren and Protopterus). The gonads are long and are cov- 



ao 



cv 



FIG. 333. Hinder part of urogenital organs of male pike, Esox lucius, after Goodrich 

 a, anus; ab, air bladder; ao, aorta; d, Wolffian duct; c, cardinal vein; g, genital duct; go, 

 genital opening; i, intestine; PC, postcardinal vein; ub, urinary bladder; uo, urinary opening- 



ered on the ventral side with lymphoid tissue. The testes in Protopterus and 

 Lepidosiren contain numerous alveoli lined with sperm-forming cells. The sperm is 

 carried into a longitudinal tubule (fig. 325) and from thence by one (Protopterus) 

 or several efferent ductules to the Malpighian bodies of the posterior end 

 of the mesonephros, the epididymis thus being posterior in position. In Ceratodus, 

 which is imperfectly known, the ductules are more numerous and the epididymis 

 is anterior. 



AMPHIBIA. The amphibians are the most typical of the anamnia, the elasmo- 



