694 KEPOKT— 1891. 



9. Experiments on Bespiration in Tadpoles of the Common Frog (liana 

 temjporaria). By Professor W. N. Parker, Fh.D. 



After referring to the great power of adaptation to external conditions seen 

 amongst ampbibious larvte, the author described some experiments on frog tad- 

 poles, which, although not yet complete, show as follows : — 



1. Soon after the lungs become functional — i.e. in tadpoles measuring more than 

 20 mm. in length — the gills are no longer sufficient for purposes of respirjvtion, 

 and the animals die in a very short time if prevented from coming to the surface 

 to breathe. 



2. If tadpoles are prevented from using their lungs from an earlier stage 

 onwards the gills remain perfectly functional, and development proceeds as usual. 

 At metamorphosis the fore limbs are slow in becoming free, owing to the retention 

 of the operculum, that on the same side as the spiracle appearing hrst. Eventually 

 a slit-Hke spiracle is present on either side. In respiration the mouth is opened 

 and closed as in the tadpole. Specimens of branchiate frogs were exhibited in 

 which the tail had shrunk to less than half its original length. 



] 0. On the Arrangement of the Living Fishes, as hased upon the Study of 

 their Reproductive System. By Professor G. B. Howes, F.L.S., F.Z.S. 



On comparing the urino-genital organs of those Osteichthyes having a non- 

 abbreviated kidney with the same organs of the higher vertebrata and the 

 Elasmobranchs, the female genital duct and the kidney are seen to be inversely 

 proportionate in length. No feature more fully characterises the development 

 of the MiiUerian duct than the accompanying abbreviation of the kidney and the 

 disappearance of its head segment. The persistence of the last-named among 

 the Osteichthyes, and its possible retention of the renal function in rare cases, 

 taken in conjunction with the mode of development of the ovary duct in these 

 fishes, point to the conclusion that the latter is in no way homologous with the 

 Mullerian duct as ordinarily understood. Balfour's belief that the genital ducts 

 are homologous in both sexes of theTeleostei is supported by the facts of anatomy ; 

 and comparison of the reproductive system of the Ganoids with that of the 

 Teleosteans shows the two to he modifications of the same common type ; and 

 the absolute structural community of the parts in the males and females of the 

 Sturiones, while further confirming Balfour's doctrine, is opposed to Jungersen's 

 implication that the subtle differences in the mode of development of the ducts in 

 the opposite sexes of the Teleostei are indicative of their non-homology. 



The facts above alluded to justify us in regarding the genital ducts of the 

 Osteichthyes not only as homologous in the two sexes and primarily independent 

 of the genital glands, but as distinct structures sui generis probably unrepresented 

 in all other vertebrates. 



The Plagiostomi and Holocephali, in which vasa eflerentia are present and the 

 kidney becomes an accessory to reproduction in the male, may be grouped together 

 into a Nephrorchidic Series, as distinguished from an Eufhorcliidic Series embracing 

 the Osteichthyes (Ganoids and Teleosteans). Comparison of the pori-genitales in 

 relation to the coalesced ureters of the Marsipobranchii with the corresponding 

 parts of the females of those Teleostei destitute of genital ducts, especially in 

 consideration of the facts concerning the development of the parts recorded by 

 Scott, Liszt, and others, supports liatbke's conclusion that the ancestors of the 

 first-named fishes must have possessed genital ducts. The Osteichthyes, although 

 specialised in respect to many features of their organisation, have, together with 

 the Marsipobranchs, retained the least modified type of urino-genital system 

 known for living vertebrates. W. N. Parker's recent and important discovery, 

 that while in Protopterus a MiiUerian duct is present vasa eflerentia are absent, 

 the testicular products being discharged through a duct more nearly comparable 

 to that of the bony fishes than to the genital ducts of any otlier vertebrates, 

 suggests that the development of vasa eflerentia and the assumption of a genital 



