4!)} Mil. .1. CIIAIIAM KIOIM! OH [Nov. l'.». 



of tli«- vievt that the possi ssionof such a network is a very ancient 

 characteristic of the gnathostomatous Vertebrata. Known long 

 to exist in Selachians, and in the Amphibia and Amniota, il is 

 now known to exisl also in Ganoids (Lejndosteus, Aciperuer, Antia) 

 and in the Dipnoi. It exists, in fact, in all the main divisions 

 excepl the Crossopterygians and Teleosts. Sorely il is more easy 

 to believe that a secondary condition has come about in the last- 

 mentioned two groups than that the same condition should have 

 arisen secondarily in every one of the other groups menti >ned ! 

 The probability of this being the case is, I believe, much increased 

 bv considerations which will become apparent later on. 



The points in the structure of the genito-urinary apparatus 

 of the Dipnoi that appear to me to have a general bearing on the 

 morphology of the male genital ducts in other fishes are two: — 



(1) The testis, of a primitive very much elongated shape, has 



become divided into two regions : — an anterior sperm- 

 producing portion, and a posterior portion which has lost 

 its sperm-producing function, has become simplified iu 

 structure, and serves with its widely expanded cavities 

 merely as a vesicula seminalis and as a duct. 



(2) The testicular network has vanished throughout the 



anterior sperm-producing portion : the posterior vesicular 

 portion, on the other hand, retains its communication with 

 the kidney apparatus near its posterior end. 



In these two features I believe we have a condition which throws 

 much light upon the condition found in Teleostean Fishes and in 

 Polypterut (as described by Budgett 1 and Jungersen 2 ), which. 

 as Jungersen pertinently points out, leads up to the Teleostean 

 condition. 



In Polypterus the testis is described as being continued hack 

 into the testis-ridge (Budgett), containing the main testis- duct, 

 and associated with this a network of irregular cavities lined by 

 cubical epithelium and giving off here and there a caeca] projection. 

 At it- hinder end the main cavity of this ridge communicates with 

 the kidney-duct near its posterior termination. 



Similarly in Teleostei Jungersen ' points out: — 



(1) That the genital duct of the male develops iu complete 



continuity with the testis ; 



(2) That the genital duct in the male develops usually not as a 



simple tubular cavity as does the oviduct, but that a 

 network of anastomosing cavities is formed : and 



(3) That the genital duct in the male usually develops its 



opening into the distal portion of the kidney-duct. 



Now the theoretical interpretation of the male genital ducts of 

 i rossopterygians and Teleosts is, I think, greatly facilitated by the 

 conditions which 1 have described as holding in Lepidosiren and 



J'ro/uj ihri's. 



1 Trans. Zool. Boc. vol. xv. Bead M»\ 8, 1900, published April 1901. 



- Zool. Anzeiger, June 14, 1900. 



- Arli. Zool.-zoot. Inst. Wureburg, ix. 1889, p. 179. 



