O przeobrazeniu aksolotla zyivionego tyroidinq. — On 
the metamorphosis of Arnblystoma mexicanum Cope fed 
on thyroidine. 
Note préliminaire 
de M lle LAURA KAUFMAN , 
présentée, dans la séance du 5 Février 1917, par M. E. Godlewski fils rn. c. 
(Planche 6). 
The larvae of Amblystoma mexicanum Cope („Axolotls“) lend 
themselves undoubtedly very well to a study of the causes of me¬ 
tamorphosis; their size makes research easy, changes evident. Their 
organs are developed before they change into terrestrial animals; 
this circumstance is of importance for the discrimination of pro¬ 
cesses connected with evolution (formation of legs, sexual matura¬ 
tion etc.) from processes of metamorphosis „sensu stricto“ (reduction 
of the gills and of the tail-fin, changes in the skin, in the eyes, 
eyelids etc.). Amblystoma mexicanum in its normal state does not 
undergo metamorphosis; inducing metamorphosis we are not acce¬ 
lerating normal changes, we rather elicit changes which the 
animal under its natural conditions would not undergo and which 
it never would have underwent without the assistance of external 
factors. Evidently here these factors are well under our control. 
Gudernatsch’s work suggested examining the influence of 
thyroidine food on the process of transformation of Amblystoma 
mexicanum. The influence of thyroidine on the metamorphosis of 
axolotls has been investigated by Laufberge r. In his experi¬ 
ments the larvae lost their gills and completed their metamorpho¬ 
sis. All larvae were very young (they were as long as 6 cm); the 
dose of thyroid-gland given was not measured. That was perhaps 
why all his animals died. 
