Dr. Burneti on the Renal Organs of the Vertebrata. 379 
at least that they are distinct organs as independent of the per- 
manent kidneys or as the ordinary Wolffian bodies of Birds an 
Mammals. 
This is a point to which I gave special attention in makin 
these investigations, and after the most careful and repeated ex- 
aminations of the larvee of Batrachia, in all their stages, I have 
wholly failed to find a structure, such as Miller has described, 
distinct from the developing kidney, and which would correspond 
to the ordinary Wolffian body. On the other hand, all that I 
have observed in this respect is, that the common duct (future 
ureter) of the forming kidney extends quite high up towards the 
cardiac region, some distance beyond the upper limit of its 
branching out into uriniferous canals. The upper end of this 
free portion of the duct is convoluted and seems to have some 
direct connection with the blood-vessels, though I have never 
here observed any thing like Malpighian bodies. As the devel- 
opment of the kidney progresses, this free extremity of the tube 
gradually disappears, and towards the end of the larval state is 
observed only in remains. In brief, then, I have observed no 
distinct, temporary urinary organs in the undeveloped forms of 
Amphibia. 
These observations, made for the most part during the summer 
of 1852, though repeated from time to time until quite recently, 
I was pleased to perceive confirmed by so excellent an observer 
as Wittich in a paper published in the antunin of the same year.* 
Wittich’s investigations have been very extended, and as far at 
least as they relate to the renal organs, furnish results much like 
my own. He found nothing in the larvee of the naked Am- 
phibia which would correspond to Miiller’s Wolffian bodies, ex- 
cepting the free prolongation upwards of the main duet or the 
ureter of the developing kidney. 
Phe doctrine here insisted upon that the true Wolffian bodies, 
or feetal kidneys, are present only in the embryos of the true Rep- 
tiles, the Birds and the Mammals, is so apposite with the results I 
have obtained from an investigation of the Allantois, that it may 
urged with an added force. In the paper already alluded to, I 
have sought to show that the Allantois is, primitively, the vesicu- 
lar expansion of the combined extremities of the ducts of the 
olffian bodies, and finally becomes the receptacular appendage 
of these organs—its contained liquid being properly urine.t But 
afterwards it subserves also another function—that of the aeration 
e blood. 
h 
Zeitsch, f. wissensch. Zool, 1v, 1852, p. 125; also, Harn- und 
: chtso yon 
lossus pictus und einiger anderer aussereuropaischer Batrachier, ibid, p. 168, 
+ Jacobson, as is well known, detected urea in the liquid contents of the 
of very young embryos. See loc. cit 
