406 FISHES CHAP. 
In Protopterus each testis is divided into an anterior sperm- 
producing part and a posterior tubular portion which has lost 
the capacity of producing sex-cells. The testicular network is 
greatly reduced, and forms but a limited connexion between the 
tubular portion of the testes and the mesonephric duct (Fig. 
233, B). If it be supposed that the testicular network became 
still further reduced so that the connexion between the testes 
and the kidney-duct took place directly through a single channel 
instead of through several, the result would be a gonoduct 
essentially similar to the male duct of an ordinary Teleost. 
Fig. 233.—Diagram to show the kidneys and gonoducts of a female Salmon (A), and of 
a male Protopterus (B). md! and md?, Anterior and posterior vestiges of the 
Mullerian duct ; ¢.¢, tubular posterior portion of the testis (¢). Other reference 
letters as in Fig. 230. (B, after Graham Kerr.) 
Should this view prove to be correct, it will follow that the 
male gonoducts of a// Fishes are differently-modified examples 
of the Elasmobranch type. But there will still remain the 
female gonoducts of Ganoids and Teleosts, which must be 
regarded as distinct from Miillerian ducts unless it can be shown 
that their different methods of development are not necessarily 
fatal to their homology with Miillerian ducts, or that both types 
of gonoduct can be derived from some intermediate type. 
Assuming that some Fishes do possess male or female ducts 
which have not been derived from the kidney system, but have 
been independently acquired, there is still the question, which 
of the two types is the more primitive, or, in other words, 
has the Elasmobranch type superseded the Teleostean, or vice 
