36 
L. Kaufman: 
The authors mentioned above have taken into consideration the 
formative influence of external conditions and paid but little atten¬ 
tion to the internal factors which regulate the duration of aquatic 
life. Chauvin mentions that axolotls undergo metamorphosis when 
they are normally hatched. Kämmerer has observed that the 
larvae of Alytes , taken out of their egg-membranes artificially, show 
a tendency to neotenia; from the investigations ofShufeldt it 
follows that young axolotls are more easily induced to undergo 
transformation than older ones. These observations however were 
of a somewhat fragmentary character; the authors mentioned above 
did not pay any special attention to the question. Changes occurring 
in amphibians undergoing metamorphosis have not been thoroughly 
investigated, though transformation is undoubtedly a most interesting 
and a quite general biological phenomenon. Episodes only in the 
process of the metamorphosis of Anura have been the object of 
some researches. Miecznikow, Loos. Barfurth and others de¬ 
scribed the changes of the resorbed tail in tadpoles; and recently 
Ratner and Reichenow investigated the degeneration of tissues 
in the intestines of the frog during transformation. In Bataillon’s 
paper we find an elaborate description of changes occurring in 
other organs of tadpoles, and also an attempt at interpreting the 
mechanism of transformation of a being adapted to aquatic life into 
an amphibious animal. Bataillon asserts that, during metamor¬ 
phosis of frogs, histolysis is not restrained to organs undergoing 
resorption (the tail, the gills), that it also takes place in the tissues 
of the organism (in the skin, the muscles, the cartilage, the intes¬ 
tines, the liver). The rate of respiration in tadpoles is accelerated 
after transformation has begun, the production of carbon dioxide 
decreases. Bataillon maintains therefore that the appearance of 
the fore limbs and the simultaneous development of the „spiracula 
complémentaires“ provoke respiratory disturbances (asphyxia); the 
accelerated rate of respiration, the retardation of the excretion of 
C0 2 , and the general histolysis leading eventually to the resorption 
of certain organs, are said to be the result of these changes ap¬ 
pearing during the larval evolution of Anura. But metamorphosis also 
occurs in TJrodela whose larvae after the development of the limbs 
remain in water for several weeks (or for several years or even 
for life, as in axolotls), and much time elapses until they lose their 
gills and fins and are transformed into terrestrial animals. Taking 
