370 RUTH B. ROWLAND 
restored between these two components, nor did the duct, 
posterior to the transplant, give any evidence of functioning. 
A sHghtly different method was apphed in a third series of experi- 
ments. The pronephros was not alone transplanted, but was 
taken together with the overlying ectoderm, the surrounding 
mesoderm, and even small portions of the ventral myotomal 
walls. This transplant was procured from another animal, and 
was transferred into a previously prepared incision and held in 
place until healed. On the next two successive days the left 
and right pronephric rudiments were removed. No appreciable 
-X. 
m^ sW" 
Fig. 10, A and B Diagrams to sliow the location and extent of operations made 
in removal of different segments of the embryonic pronephros. In A the seg- 
ment removed, x, was a part or the whole of the U-shaped tubule anterior to the 
segmental duct. In B the segment removed, x, consisted of a part or the whole 
of the rudiment of the funnels. 
difference was noted in the ensuing condition of this series, and it is 
safe to conclude that under these circumstances the excised tubule 
is unable to readjust itself and function in its new location. 
Interruptions to the development of the pronephros by a less 
radical operation also go to strengthen the belief that the regen- 
erative capacity of the kidney tubule is either very limited or 
very slow in taking place. ^ In a number of embryos from which 
one pronephros had been extirpated, a small portion of the 
opposite rudiment was also excised. The segments removed (x) 
were at two levels, as designated in figure 10, A and B. The 
funnels were undisturbed in one group (A), a short piece of the 
^ This does not apply to the coelomic epithelium which lines the nephrostomal 
opening, as will be shown in a later section. 
