376 Dr. Burnett on the Renal Organs of the Vertebrata, 
manent renal organs, these last may be only persistent Woiffian 
bodies, but this point will receive our attention at a future time. 
Wherever occurring, these Wolffian bodies present the same 
unvarying form and type of structure; their mode of develop- 
ment [ have found to be equally invariable, whether occurring in 
Reptiles, Birds, or Mammals. They always make their appear- 
ance during the very earliest phases of development of the em- 
ryo, and, with the neg te of the heart, are the first organs 
formed in the abdominal ca 
As I have studied these liens of development in Birds more 
earefully than in the other classes, [ will describe them as ob- 
served in the chick; and this description wiil include what belongs 
to these organs in Reptiles and Mammalia, in all their essential 
details. 
In the Chick, there appears, at about the fiftieth (50th) hour of 
incubation, a bitte on each side of, and lying close to, the vertebra 
column; this line extends from near the region of the heart to 
the caudal vertebrae, and is composed of a collection of nucleated 
cells which soon beeome arranged so as to forma tnbe; this tube 
is the basis of the future Wolffian body. At this stage of devel- 
opment there is observed, then, a simple tube on each side of 
the vertebral column ; but a few hours nlite the surface of the 
tube becomes nodulated at regular intervals on its inner surface. 
These nodulations are the beginnings of a series of eversions 
from the main tube which soon therefore ape a digitated appear- 
ance—each of the finger-like prolongations being a future urinif- 
erous tube. These prolongations having been formed from with- 
out inwards, the original tube, which now has become a common 
se lies upon the external side, aud the former overlap the ver- 
al column. 
This formation of tubes by deverticula from a main one, con- 
stitutes the first phase in the development of this organ as a coml- 
und structure. - The second phase is the formation of a direct 
connection between the blood-vessels and these near pie 
tubes, so that an eliminating function may b rformed. This 
occurs at about the sixtieth (G0th) or sixty-fifth (65th) hout of 
incubation. At this time, the free extremities of some, but not 
all, of the newly-formed tubes become enlarged aud dilated into an 
infundibuliform body which, together with its attached tube, te 
sembles a flask with a very long neck. Jn this dilated extremity 
of the tube, a knot of blood-vessels is formed anew from epit 
lial cells ; ‘this ones in a manner so beautiful that I digress here 
for its more careful descr 
This infundibuliforn or teed end of the tube is nothing but 
the tube at this point taking on a little on proms - jt is there- 
fore lined, like the tube itself, with a layer of epithelial 
These cells, by a more or less linear arrangement, form form a 
