256 



DIPNOI. 



Urinogenital Organs. The kidneys* are without nephro- 

 stoniata in the adult ; they are elongated glands not differentiated 

 into meso- and meta-nephros. Each of them has a ureter which 

 either joins its fellow before opening into the cloaca (Ceratodus) 

 or the ureters open separately into a cloacal caecum 

 derived in development from the fused hind ends of 

 the longitudinal ducts. The larva possesses a pro- 

 nephros on the Amphibian type with two funnels and an 

 elongated glomerulus contained in an incompletely separated off 

 portion of the body-cavity. The ovaries and testes are elongated 

 bodies. The oviducts are convoluted tubes opening anteriorly 

 and far forward into the body cavity and joining behind to open 

 into the cloaca just in front of the ureters. The testis has a 



2 3 



^^&Z^. 



iiiiitii^^ 



Fig. 133.— Lonttitudinal vertical section tlirough the brain of Protopterus (after Burckhardt). 

 / choroid plexus of 4th ventricle ; 2 cerebellum ; -3 mesencephalon ; 4 posterior ccm- 

 missure ; o pineal stalk ; 6 superior commissure ; 7 velum transversum ; S pineal body ; 

 .9 choroid plexus ; 10 corpus callosum ; 11 anterior commissure ; 12 optic chiasma ; 13 

 saccus vasculosus ; 14 pituitary body ; IS spinal cord. 



longitudinal duct extending along its whole course. This duct 

 communicates with the tubuli seminiferi on the one hand and by 

 a number of transverse tubes with the hinder part of the kidney. 

 It ends blindly in front and behind, and has been fully made out 

 in Lepidosiren ; it probably exists in Ceratodus. A similar duct 

 is described by Parker in Protopterus, where it is said to open 

 into the cloaca and not to communicate by transverse tubes 

 with the kidney. This is however denied by Kerr. The male 

 possesses a well-marked vestige of the oviduct. 



The egg is of considerable size and undergoes complete unequal 

 cleavage. The early develoj)ment is very like that of Amphibia 



* Kerr, Proc. Zool. Soc. 1901, p. 484. 



