REMOVAL OF PRONEPHROS OF AMBLYSTOMA 383 
10. Anterior and posterior nephrostomal funnels are regen- 
erated from the coelomic endothelium in a large proportion of 
operated embrj'os, 
11. The segmenta' duct on the operated side shows great 
variation in development, ranging from a condition in which the 
lumen, though small and flattened dorsoventrally, appears 
throughout the entire length, to a condition where only the 
occasional presence of a few degenerating cells indicates the 
location of the atrophied duct. 
12. Increased activity of a single kidney also has a definite 
effect on the segmental duct of the same side. Cross-sections 
of the duct of an individual with unilateral operation, when com- 
pared with either of the ducts of a normal larva of the same 
age, show a marked increase in diameter. 
13. In embryos from which the heart rudiment has been 
remo\'ed in a very early stage, the initial development of the 
glomeruli is normal. Subsequent distention of the aorta tears 
the cells apart and they soon lose their identity as lateral capil- 
lary tufts. 
