34 
L. Kaufman: 
Camerano (with Chauvin) considers that the quantity 
of water is one of the factors which regulate metamorphosis in 
Urodela as well as in Anura. In large quantities of water, plastic 
organisms become adapted to the conditions of the surroundings 
and may fail to undergo metamorphosis at all; polymorphic forms 
appear then, as in axolotls and in Molge alpestris. Kämmerer says, 
neotenia is caused by abundance of water, its depth being of no 
importance for the course of metamorphosis. It seems that quality 
rather than quantity of water plays a rôle in these changes; a con¬ 
clusion which follows also from the investigations of Chauvin. 
Gradual diminution of the quantity of air present by replenishing 
the vessel with boiled water was one of the methods of procedure 
through which Chauvin induced axolotls to undergo metamor¬ 
phosis. Gadow believes that abundance of water of good quality 
permits axolotls to remain during the whole of their life in the la¬ 
kes surrounding Mexico City. Metamorphosis is therefore influenced 
not by the water itself, but by quantity and quality of contained 
air (i. e. by the abundance of 0 2 and the scarcity of C0 2 ). The 
same conclusion was secured by the experiments of Shufeldt 
who observed that axolotls undergo metamorphosis more easily in 
water containing small quantities of air. The interdependence be¬ 
tween the amount of air contained in water and the larval stage 
in amphibians was also ascertained by Kammerer’s investiga¬ 
tions on the mode of reproduction of Alytes obstetricans and by 
those made by Wintrebe.rt on the influence of the absence of 
respiration on the metamorphosis of Anura and on adaptation of 
organisms to surroundings. Wintrebert put tadpoles into a met¬ 
allic cage at the bottom of a tube containing 100 1. of water; 
a current of fresh water was flowing close to the cage. The meta¬ 
morphosis of 25 tadpoles in these experiments occurred later than 
that of four tadpoles used as standard. This experiment (which re¬ 
quires repetition with a greater amount of specimens) appears to 
show that abundance of fresh water in the presence of an ade¬ 
quate quantity of air delays the processes of metamorphosis. These 
results are contrary to other observations by Wintrebert, on 
the influence of surroundings containing much C0 2 on metamorphosis. 
He finds that metamorphosis not only is not accelerated by C0 2 
(as might have been expected from the results of previous in¬ 
vestigations) but, on the contrary, even delayed. But as the tadpoles 
