62 
L. Kaufman: 
tbe epithelium of larval skin, with fig. 8, the epithelium of the 
skin of transformed Amblystoma, as well as of phot. 5 of one fold 
of a larval intestine with phot. 6 of an analogous fold of the ter¬ 
restrial form, made at the same enlargement, illustrates the above 
statement. In the tissues of animals fed on thyroidine far more 
nuclei are lying than in the same surface in normally fed specim- 
Fig. 2 a. 
ens. Romeis observed considerable retardation of regenerative 
processes in tadpoles fed on preparations of the thyroid gland. The 
above-stated change of tbe plasma nuclear ratio elucidates the cause 
of the retardation of evolutionary processes. 
It has been ascertained by Godlewski that in embryonal tis¬ 
sues as well as in those undergoing regeneration there is more 
plasmatic ar^d less nuclear substance than in tissues in stationary 
state. It has been shown that these changes in the relation of nucleus 
to plasma elicit evolutionary processes. On the other hand, the 
fact observed by Romeis that, in tadpoles fed on thyroidine, the 
amputated tail underwent slight regeneration, in connection with 
my observation that, in cells of axolotls fed on extracts of thyroid 
gland, the plasma-nuclear ratio is considerably altered to the ad¬ 
vantage of the nuclei, proves that the preponderance of nuclear 
over plasmatic substance produces retardation of the processes of 
regeneration. 
