METANEPHRIC ANEAGE OF CHICK 
411 
granuloblastic transformation of the loose embryonic mesen¬ 
chyme in chick embryos was experimentally produced, the stroma 
of the meso- and metanephros being included in the general 
reaction. The development and differentiation of the nephric 
tubules in these embryos proceeded, however, in the usual way 
without any apparent disturbance. New nephric tubules con¬ 
tinued to form, but were separated by strands of granuloblastic 
tissue. In the metanephros the granuloblastic metaplasia was 
less marked than in the mesonephros. Contrary to what was 
observed in the mesonephros, comparatively few mobile cells 
developed from the apparently uniform mesenchyme of the 
metanephrogenic cord. The question as to whether the nephro¬ 
genic tissue consists of two substantially different tissues (an- 
lages of renal epithelium and stroma) appearing under the 
aspect of morphologically identical cells, was left undecided 
by Danchakoff: 
It is true, that the factors for the granuloblastic differentiation of 
the mesenchymal stroma become, under the present experimental 
conditions, so powerful as to transform a large amount of mesenchymal 
cells into granuloblasts even in a region of the organism in which 
granulopoiesis has never occurred in a typical development. It would, 
therefore, be only natural to expect that, if the nephrogenic tissue proper 
possessed a potentiality for granuloblastic differentiation, it would 
have manifested it under the present condition. The granuloblastic 
potentiality may, however, still be a property of the nephrogenic tissue, 
but the factors for the specific organization of the nephrogenic tissue 
into the renal epithelial tubules, which are unknown to us, may be of a 
more decisive nature for their realization. 
More information concerning the development and differ¬ 
entiation of the nephrogenic anlage may be obtained by a study 
of the development of the anlage isolated from its normal en¬ 
vironment and allowed to grow outside of the organism. 
Champy studied in detail the behavior of adult and embryonic 
kidney tissue outside the organism. Using Harrison’s tissue 
culture method as modified by Burrows and Carrel, he observed 
first an intensive proliferation of the cells of the renal tubules, 
followed by disintegration of the tubules to form cords of epithe¬ 
lial cells. According to his observations, the cords of epithelial 
