548 PEOr. G. B. HOWES ON SOME 



formed ducts of the males and of those females in whicli they are 

 completely closed are well known to afEect the opposite sexes 

 indifferently ; these weighty facts of anatomy bear out Balfour's 

 deduction {cf. infra) that the ducts are homologous in both 

 sexes, and completely override the force of Jungersen's dis- 

 covery. By a Miillerian duct we understand one invariably 

 arising far forwards, either in relation or immediate proximity to 

 the head kidney, when such exists, and becoming for the most 

 part completed by a process of backward extension. The re- 

 searches of Jungersen show clearly that the one distinguishiug 

 feature of the Teleostean genital ducts is their restriction, alike 

 in origin aud relationship, to the posterior genital region ; and, 

 whatever may be said for their supposed homology in the two 

 sexes, this fact is, to my mind, fatal to the supposition that that 

 of the females represents a Miillerian duct as ordinarily under- 

 stood. 



Jungersen's Teleostean's genital duct arises, like Balfour and 

 Sedgwick's ijosterior segment of the Chick's Miillerian duct, late, 

 and in juxtaposition to the base of the Woli£an or segmental duct. 

 The Miillerian duct of the Anura is asserted by Hoffmann * to 

 arise for the most part as a backwardly extending derivative of the 

 peritoneal epithelium. Eiirbringer describes the Miillerian duct 

 of the Urodelaf as formed {Salamandra) of an anterior seg- 

 ment derivative of a thickened aud backwardly extending portion 

 of the peritoneal epithelium, aud a posterior one arising as a 

 solid product of the wall of the pro-renal duet $. These facts not 

 only strengthen the conclusion that the female genital duct of 

 the Amniota and Amphibia is in all probability a compound struc- 

 ture, but, in view of the isolated position of the Elasmobranchii 

 already referred to on p. 546, they suggest that ifc may not be 

 serially homologous for the three groups. Upon this possibility 

 future investigation must decide. The facts, taken in conjunc- 

 tion with those to which I have herein drawn attention, point, I 

 believe, most markedly, to another and simpler conclusion, viz. : 

 that the genital ducts of the Teleostei are in both sexes distinct 

 from tliose of Elasmobranchs, Amphibians, and Amniota, and that 



* Zeitsclir. f. wiss. Zool. Bel. xliv. p. 594 (1886) {cf. Marshall & Bles, 

 q^. cit. pp. 142-143). 



t Morph. Jahrb. Ed. iv. p. 31 (1878). 

 \ Cf. V. Wijhe & Juiigei'sen, q?j. cit. 



