50 Nature of the Formative Stimulus 
This would indicate then that the greater phagocytic 
activity would be not so much the cause as rather the 
effect of the diminution of the vital resistance of the 
organ. And this latter would seem necessarily to be 
due exclusively to the fact that the organ itself would 
be at this ontogenetic stage abandoned by the particular 
energy which had formed it, and which up till now 
had maintained it in full vital activity, and which now 
has not indeed ceased to exist, but has turned to other 
regions. This transference of cellular material in process 
of disintegration to other organs and tissues in process 
of formation would seem in fact to demonstrate that 
simultaneously with the diminution or the cessation of 
the trophic stimulus in one given region there appears 
an increase of that stimulus in another region. 
This utilization, as nutritive material, of the substance 
of cells which are disintegrating is rendered necessary by 
the fact that animals during their metamorphosis take 
almost no nourishment. It follows that, if the nutritive 
material which the abandoned parts give up to the parts 
now more abundantly infused with trophic energy, should 
be insufficient at the normal rapidity of disintegration, 
the disappearance of the tissues must be accelerated. This 
is indicated by Osborn’s researches upon the influence of 
fasting upon metamorphosis, from which it appears that 
it is appreciably accelerated by inanition, just because of 
the more rapid reduction and absorption of the organs 
about to disappear.?® 
In the disappearance of the tail of the tadpole one has 
not a senile but rather a premature involution of tissues, 
26Qsborn: Alte und neue Probleme der Phylogenese. Ergebn. 
d. Anat. u. Entwicklungsgesch., herausg. v. Merkel u, Bonnet. Bd. 
III. 1893. Wiesbaden, Bergmann. 1894. P. 1098. 
