Observations on the development of the excretory system in Turtles. 7Q3 



The researches of Hoffmann, Wiedersheim and myself show in- 

 terestiog similarities in regard to the pronephric region; with regard 

 to the basis of the mesonephros and the formation of tubules, my 

 results correspond with Hoffmann's save that in Plafypeltis one does 

 not see the early separation from the side plates found by him in 

 Lacerta. Hoffmann and Wiedersheim derive the secondary tubules 

 of the mesonephros by branching , from the primary tubules, but my 

 material shows at least one entirely independent series of secondary 

 tubules. Braun and myself have obtained results entirely at variance 

 with those of Wiedersheim and Hoffmann as to the origin of the 

 metanephros finding no direct connection with the mesonephros, but 

 the conditions in the form studied by Braun are entirely different 

 from those I find in Platypeltis. 



In comparison with the work on other orders, it will be seen that 

 my results as to the origin of pro- and mesonephros are entirely in 

 harmony with those of Rückert and Van Wijhe in their work on 

 the shark, and support the same conclusions, although, as Hoffmann 

 also noticed, the lumina of the tubules, in our material do not cor- 

 respond with those of the somites. 



There is nothing in my material which would justify the title of 

 "Vornierenkammer" as found by Maas and Semon in Myxine. Although 

 the lacunae of the pronephros sometimes anastomose — they run 

 irregularly through the body tissue near the tubules and are not 

 circumscribed or confined by a wall of any sort except the wall of 

 the coelom. When they acquire tissue, possibly from the combi- 

 nation with mesonephric elements, they seem to push out further 

 into the body cavity and from more or less continuous external 

 glomera, largest near the funnels. 



From the fact that I find no glomerulus in the pronephros (save 

 exceptionally in somite X as explained above) and no tubules opening 

 into the body cavity in the mesonephros, it is clear that I find no 

 "Innen- und Aussentrichter" as described by Semon, '92 (tab. 3, fig. 7), 

 and discussed by Felix, in: Anat. Anz., V. 13. 



It seems to me that the most important bearing which my work 

 has on that of Price is in the fact that it shows how early the marks 

 distinguishing pro- and mesonephros may be lost, though clear in the 

 beginning, and that, therefore, since he says, '97, p. 212: "Even in 

 the youngest embryo the myotomes are entirely separated from the 

 unsegmented portion of the coelom and throughout the greater part 



Zool. Jahrb. XUI. Abth. f. Morph. 4g 



