704 



GANOIDEI. 



is more probably a case of degeneration, as is indicated by the 

 presence of ducts in the male Salmon and in forms nearly allied 

 to the Salmonidae. 



The coexistence of abdominal pores and generative ducts in 

 Mormyrus appears to me to demonstrate that the generative 

 ducts in Teleostei cannot be derived from the coalescence of the 

 investment of the generative organs with the abdominal pores. 



Ganoidei. The true excretory gland of the adult Ganoidei 

 resembles on the whole that of Teleostei, consisting of an 

 elongated band on each side the mesonephros an anterior 

 dilatation of which probably represents the pronephros. 



There is in both sexes a Mullerian duct, provided, except 

 in Lepidosteus, with an abdominal funnel, which is however 

 situated relatively very far back in the abdominal cavity. The 

 Mullerian ducts appear to serve as generative canals in both sexes. 

 In Lepidosteus they are continuous with the investment of the 

 generative glands, and thus a relation between the generative ducts 

 and glands, very similar to that in Teleostei, is brought about. 



Posteriorly the Mullerian ducts and the ducts of the meso- 

 nephros remain united. The common duct so formed on each 

 side is clearly the primitive segmental duct. It receives the 

 secretion of a certain number of the posterior mesonephric 

 tubules, and usually unites with its fellow to form a kind of 

 bladder, opening by a single 

 pore into the cloaca, behind 

 the anus. The duct which 

 receives the secretion of the 

 anterior mesonephric tubules 

 is the true mesonephric or 

 Wolffian duct. 



The development of the 

 excretory system, which has 



been partially worked out in 



. . , T . , j 



Acipenser and Lepidosteus , 



is on the whole very similar 

 to that in the Teleostei. The 

 first portion of the System to 



FIG. 396. SECTION THROUGH THE 

 TRUNK OF A LEPIDOSTEUS EMBRYO ON 

 THE SIXTH DAY AFTER IMPREGNATION. 



mc - medullary cord; ms. mesoblast; sg. 

 segmental duct ; CM. notochord ; x. sub- 

 notochordal rod; hy. hypoblast. 



1 Acipenser has been investigated by Fiirbringer, Salensky, Sedgwick, and also 

 by myself, and Lepidosteus by W. N. Parker and myself. 



