of Dipnoan Fishes. 331 



slight aggregations of nuclei and protoplasm in the mesoblast 

 internal and slightly dorsal to the archinephric duct. It is re- 

 markable that the tubules, at first strictly metameric, become at 

 a very early stage increased in number so as to be about twice 

 as numerous as the myomeres in the same region. Each tubule 

 rudiment assumes the form of a (j, the longer limb coming into 

 contact with the wall of the archinephric duct. About stage 31 

 a lumen appears in the better developed rudiments, which thus 

 become tubular. The outer end of the tubule opens into the 

 archinephric duct. The inner end, the end of the shorter limb of 

 the [), expands, becomes thin walled and soon becomes dilated to 

 form a chamber which in a transverse section appears nearly as 

 large as the section of the archinephric duct. The cavity in 

 question is the rudiment of the Malpighian capsule, and thus the 

 capsular coelom in Lepidosiren develops secondarily as a cavity in 

 the mesoblast, quite distinct from the perivisceral cavity. In 

 Lepidosiren peritoneal funnels connected with the mesonephros 

 do not exist at any period. For some time there is no glomerulus 

 projecting into the capsule, but by stage 35 the glomerular pro- 

 jection is quite distinct. 



Testicular network of Dipnoi. 



The existence of a connexion between testis and mesonephros 

 was first established by Ehlers for Lepidosiren. Semon has recently 

 chronicled the discovery of spermatozoa in the Malpighian cap- 

 sules of Ceratodus — pointing to a connexion in that Dipnoan. 

 I have myself described the testicular kidney connexion in Pro- 

 topterus, and I have also worked out in detail and figured for the 

 first time the precise relations in the adult male Lepidosiren. 



These relations may be shortly summarised as follows : 



In Lepidosiren the very much elongated testis is divided into 

 two regions — a larger formative region somewhat cylindrical in 

 shape and lying immediately ventral to the mesonephros, and a 

 shorter, much narrower, vesicular region which, imbedded in 

 a sheath of dense connective tissue, similarly lies ventral to and 

 closely apposed to the ventral edge of the kidney. The con- 

 nexions of testis with kidney are limited to the posterior portion 

 of the vesicular region, whence about half-a-dozen vasa efferentia 

 pass into the substance of the kidney. Here they break up into 

 branches which open into the cavities of Malpighian capsules. 

 From these the spermatozoa reach the cloaca by the kidney tubules 

 and Wolffian duct. 



In Protopterus essentially similar conditions hold, modified 

 slightly by the fact that in the fully-developed Protopterus the 

 kidneys and also the vesicular portions of the testes have become 



