49S OX LEPIDOSIREM AND PROTOPTKIIUS. [Nov. 19, 



as affording a possible explanation of the conditions occurring in 

 Teleosts. 



Summary. 



The more important features in the morphology of the male 

 urogenital system of Lepidosiren and Protopterus maybe summarized 

 as follows : — 



1. The testis is very much elongated and is divisible into an 



anterior formative and a posterior vesicular and conducting 

 region. 



2. The posterior part of the vesicular region is connected with 



the tubules of the hind end of the mesonephros, winch serve 

 for the passage of the genital products. 



3. In Protopterus the testis is connected with the kidney only 



at its extreme tip ; in Lepidosiren there is a series of about 

 half a dozen segmentally arranged vasa efferentia which 

 open into Malpighian capsules. 



4. In Protopterus the hind genital region of the kidneys is 



clearly marked off from the rest, and in this region the 

 kidneys are fused across the middle line ; in Lepidosiren 

 there is only a slight attempt at this differentiation, and 

 the kidneys of the two sides are posteriorly, as elsewhere, 

 quite distinct. 



5. The Wolffian ducts open in the adult male by a common 



(Protopterus) or by two separate {Lepidosiren) papilla; into 

 the distal portion of the cloacal caecum, which is morpho- 

 logically a urogenital sinus formed in ontogeny as a 

 dilatation of the fused, but originally separate, posterior 

 portions of the Wolffian ducts. 



EXPLANATION OF THE PLATES. 



The lithographic illustrations on Plates XXVII. and XXVIII. have been 

 drawn by Mr. E. Wilson from reconstructions by the author of his camera- 

 drawings according to the method described in Quart. Journ. Micr. Sci. 

 vol. xlv. p. 5. 



Plate XXVII. 

 Fig. 1. View from mesial aspect of reconstruction of the hind end of testis and 

 kidney of an adult, but not breeding, Lepidosiren. The testis is shown 

 yellow, the kidney blue. (In breeding specimens the testis extends 

 much further back.) 



C.t. Collecting- tube of kidney. Gl. Malpighian body. K„. Portion 

 of kidney which becomes enlarged during breeding-season (posterior 

 epididymis or hypodidymis). T r Formative region of testis. T.,. Vesi- 

 cular region of testis. V.E. Vas efferens. W.P. Wolffian duct. 



Plate XXVIII. 



Fig. 2. View from behind of a thick slice of the hinder portion of the vesicular 

 region of the testis of a breeding male Lepidosiren with its accompanying 

 mass of kidnev-tubules. 



K, Kidney. T„. Testis. V.A. Afferent vein. W.D. Wolffian 

 duct with collecting-tube opening into it. 

 Fi;.'. 3. Corresponding view of fused posterior portions of kidneys (hypodidymis) 

 of Protopterus — collecting-tubes &c. of kidney coloured blue, testis 

 and vasa efferentia yellow. 



M.D. Fused hind part of Mullcrian ducts. T,. Posterior ends of 

 testes meeting in mid-line. V.E. Yns efferens. W.D. Wolffian duct. 



