l90l.] LEPIDOSIKEN 7\.AD PKOTOPTEIIUS. 495 



1 start from the standpoint of one wbo believes that the 

 two great products of the coelomic Hning (i. e. the genital and the 

 excretory products) made their way originally to the exterior by 

 the same mode of exit — by the nephridial openings \ and that 

 the general course of subsequent evolution has probably as regards 

 the genital products been such as to keep or make their mode of 

 exit as direct and simple as possible, rather than snch as to make 

 their exit more and more complicated and difficult as some 

 zoologists Avould have us believe. 



The condition in Lepidosteus or Acipe.nser may be looked upon 

 as relatively primitive amongst tishes. Here testis and kidney are 

 alike elongated and vasa efferentia pass off along the whole length 

 of the testis to the greater part of the length of the kidney. 



In Lejyidosiren, as above described, the testis has become divided 

 into two regions, a formative and a vesicular, and the connection 

 between testis and kidney has become restricted to the posterior 

 portion of the vesicular region. 



In Protopterus we find again the division of the testis into 

 formative and vesicidar regions, but now the communication of 

 testis-cavity with kidney is still further restricted to the extreme 

 hind end of the testis. 



This, it seems to me, is but a stej) from what has been described 

 for adult Crossopterygians, where again we find a division of the 

 testis into a formative and a conducting region, the latter 

 communicating at its extreme hinder end with the kidney-duct, 

 no longer, ho\^ever, through complicated kidney-tubules but by a 

 simple direct opening^. 



I'inally, as Jungersen has well pointed out and has been shown 

 in resume above, the Teleoslean condition is naturally derivable 

 from that in Folypterus. 



According to the facts and views expressed in this paper ^, the 

 genital ducts of male Granoids, Dipnoans, Crossopterygians, and 

 Teleosts would fall into some such scheme as that expressed in 

 the accompanying rough diagram (p. 496). 



In conclusion, it is only fair to state that while the facts 

 described above are in great part new, the morjjhological hypothesis 

 which they are held to support was suggested long ago by Semon' 



' Budgett is led by bis studies ou Folypterus lo believe that the aiTangement 

 there is a primitive one, and to side witb those who believe that the connection 

 betAveen gonad and kidney is secondary. Trans. Zool. Soc. vol. xv. p. 330. 



- Exactly as has apparently coine about in Discoglossus amongst anurous 

 Amphibians — the surviving connection being, however, in this latter case, 

 anterior instead of posterior. 



^ It will be seen that this view of the morphology of the Teleostean male 

 genital duct differs in some essential particulars from that of Jungersen. 

 He points out that in Lepidosteus and Aci2}enser the testicular network opens 

 into the Malpighian capsules, in Amia into the tubule below the capsule 

 or into the kidney-duct direct. In Amia, as compared with Lepidosteus and 

 Acipenser, the openings of the testicular network into the kidney-system may 

 be regarded as having migrated down the tubule in the direction of the external 

 opening. Let such migration continue until they opened close to the exterior, 

 and a condition resembling that of Teleosts would be reached. (Zool. Anz. 

 Ed. xxiii. p. 332.) 



■* Bauplan dcs Urogenitalsystems der Wirbelthiere : Jena, 1891. 



33* 



