METANEPHRIC ANLAGE OF CHICK 
429 
lack of functional stimulus. But, despite lack of functional 
stimulus, cultures of the metanephros in the allantois attain a 
high degree of differentiation. It is possible that the different 
results obtained by Champy and myself may be due to a dif¬ 
ference in the milieu in which the cultures were planted. A 
tissue possessing the potency will differentiate into nephric 
tubules, provided the conditions for its growth and differentiation 
are favorable. Under other conditions, this process may not 
take place, and even a tissue already specialized may lose its 
specific structures, as Champy seems to have shown. 
2. A digestive power is revealed by the ureteric epithelium 
which may be seen to ingest and digest red blood corpuscles. 
Unimportant as it may seem, the observation on the phagocytic 
and digestive activity displayed by the epithelial cells of the 
collecting tubules may prove of interest in view of the vast role 
of digestive activity recently attributed to the general mesen¬ 
chyme (Danchakoff, ’21). This power of digestion may sometime 
in the future be recognized as an active and simple agent in the 
so-called defenses of the organism. In this particular case a 
specialized mesodermal cell, the epithelial cell of the collecting 
tubules, exercises phagocytic and digestive activity. Other 
apparently specialized cells in the organism, for example, endo¬ 
thelial and mesothelial cells, although in the form of epithelial 
membranes, retain and exercise to a considerable extent the 
fundamental biological property of digestion. 
3. The stroma of the grafted anlage develops along lines 
different from that characteristic of its normal development. 
Normally this tissue gives rise to sparse connective-tissue cells; 
in the grafts it is transformed into large, scattered foci of granu- 
loblastic tissue. The granuloblastic activity displayed by the 
loose mesenchyme of the metanephric anlage in these grafts 
affords additional evidence for the equivalence of the mesenchyme 
and for its polyvalency in the different parts of the organism. 
In this instance the granuloblastic differentiation of the 
mesenchyme is the more interesting since, of all regions of the 
embryo’s body, the mesenchyme of the metanephros has shown 
itself the least responsive to this change after grafts of adult 
