Dr. Burnett on the Renal Organs of the Vertebrata. 383 
the whole organ much the same lobulated, arborescent structure 
as that of the chick—although the plumate arrangement of the 
terminal tubes is not here present. In both the Cartilaginous and 
the Osseous Fishes, the functional or secreting structure is, as far 
as I have observed, always the samie; that is, the tubes invariably 
terminate each in a well-formed Malpighian body. 
In the Amphibian Reptiles, the kidneys quite closely resemble 
those of Fishes, yet simulating even more closely than these, 
the general character of the Wolffian bodies. They present little 
tendency to an aborescent structure, the tubes of the main duct 
rarely dividing but rather forming convolutions, and ending inva- 
riably, according to my own observation, in Malpighian bodies.* 
These Malpighian bodies, together with their adjacent portion of 
the uriniferous tube, are lined with long lash-like cilia, the ever 
constant, rapid action of which, waving towards the outlet, pre- 
Sents a beautiful aspect. ‘The use of these cilia is, evideutly, to 
direct the course of the current out of the Malpighian body, 
therby keeping this last in a free, unobstructed state. In the true 
Reptiles, the development of the kidney is arborescent as in Birds, 
and in the Serpents the lobules thus formed remain more or less 
Separate through life. ‘This is also the case, but in a less degree, — 
in the Chelonioide. 
delicate anastomoses bring every such cecal secreting tube within 
the influence of a blood vessel.t 
n the Chelonioide, the kidneys quite closely resemble, in every 
Point of view, those of Birds. The uriniferous tubes have the 
same form of distribution and terminate always, each, in a Malpi- 
. Shian body. 
_ As for these organs in the Birds, I have described their pecu- 
liarities in speaking of the chick, and have only to add that 
throughout the entire class there seems but little or no variation. 
In Mammalia, the course of development followed is like that 
observed in Birds, but the subsequent changes by which the organ 
comes more compact, often entirely conceal the original forms. 
By observations upon very young embryos in the different fami- 
_* For representations of the intimate structure of the kidneys of Amphibia, see, 
‘specially, Wittich. loc. cit. Taf. ix. 
anh emer is, as I have lately observed, a similar relation between the blood-vessels 
Snd the terminal exca of the poison-gland of the Rattle-snake (Crotalus—a kind of 
Rete mirabile. 
° 
