60 ï. H. BURLEND, 



differentiated into an upper small swollen "inner pronepliric chamber" 

 (inneres Vornierenkämmerchen) and a lower "neplirostomal canal" 

 (primäres Nephrostomalkanälchen) (see Felix (30), Fig. 43 a — c). 



Into the inner pronephric chambers project "internal glomeruli'' 

 as in the mesonephros, and there may also be "external glomeruli" 

 projecting into the coelom between the pronephric nephrostomes 

 and the Radix mesenterii. 



a) Evidence that the anterior pronephric tubules 

 do not arise from the nephro tome. 



There seems to be no doubt — either in the earlier embrj'os 

 where the precise limits of the nephrotome are not established, or in 

 the somewhat later embryos in which the position of the nephro- 

 tome is well established — that the primitive kidney groove in 

 Chrysemys is at first a hollow outgrowth from the somatopleuric meso- 

 derm of the lateral plate. It is also clear that the primitive condition 

 of this groove is disguised very early, for we find it in the condition 

 of a solid outgrowth from the somatic mesoderm very frequently in 

 the posterior region of the pronephros in Chrysetnys. 



GoETTE also finds a hollow groove-like rudiment of the pronephros, 

 which Felix explains away as follows: "Bei Bombinator igneus 

 giebt GoETTE keine solide Anlage des Vornierenwulstes, sondern eine 

 Ausfaltung der Somatopleura an, dieser Widerspruch erklärt sich 

 leicht aus dem Umstand, daß Goette nicht die allerjüngsten Ent- 

 wickelungsstadien beobachtet hat." 



It seems almost unnecessary to remark that if the groove was 

 there at all it needs explanation, and that this cannot be done by 

 refusing to recognise any results which do not fit in harmoniously 

 with theoretical views which are still tentative. 



Shipley (1888) derives the pronephros (in the lamprey) from a 

 groove in the parietal peritoneum. The groove closes later and 

 leaves four or five openings which become the pronephric ciliated 

 funnels or nephrostomes. 



Goette (1890) confirms the fact that the rudiment of the pro- 

 nephros in the lamprey consists of a groove-shaped evagination of 

 the somatopleure (somatic mesoderm). 



The origin of the pronephric rudiment in Chrysemys, from the 

 somatic mesoderm of the lateral plate and not from the nephrotome, 

 is in complete accordance with the researches made on the kidney of 

 many other Vertebrates. Perhaps the divergence of views on this 

 matter arises to some extent from a failure on the part of some 



