CHAPTER XII.

THE ORGANS OF EXCRETION, pp. 479-520.

Previous investigations. _Excretory organs and genital ducts in adult._ _In male._--Kidney and Wolffian body. Wolffian duct. Ureters. Cloaca. Seminal bladders. Rudimentary oviduct. _In female._--Wolffian duct. Ureters. Cloaca.--Segmental openings. Glandular tubuli of kidney. Malpighian bodies. Accessory Malpighian bodies. Relations of to segmental tubes. Vasa efferentia. Comparison of Scyllium with other Elasmobranchii. _Development of segmental tubes._ Their junction with segmental duct. Their division into four segments. Formation of Malpighian bodies. Connection between successive segments. Morphological interest of. _Development of Müllerian and Wolffian ducts._ _In female_--General account. Formation of oviduct as nearly solid cord. Hymen. _In male_--Rudimentary Müllerian duct.--Comparison of development of Müllerian duct in Birds and Elasmobranchii. Own researches. Urinal cloaca. _Formation of Wolffian body and kidney proper._--General account. Details of formation of ureters. _Vasa efferentia._--Views of Semper and Spengel. Difficulties of Semper's views. Unsatisfactory result of own researches. General homologies. _Résumé._ Postscript.