53i 
1884.] 
and the Correlation of Organs. 
lapse of three years Miss von Chauvin induced two speci- 
mens to return to their original element, and by the appli- 
axolotls 0 Sultab e means the y again become complete 
rpnol't J* tollman n has seen such animals which have thus 
repeatedly passed through the most extreme range of a 
veitebiate organ^m. He shows also (in the “ Zoologischen 
nzeigei ) that European Batrachians also possess an ex- 
traordinary range of adaptability. It has been long ago 
obseived that, their larv^ hybernate as such, and then 
leach a very considerable magnitude. Prof. Pfluger has 
observed them hybernating at Bonn and Prague/ others 
give an account of the hybernation of Tritons and of certain 
Anoura, such as Ram esculenta and Alytes. Kollmann has 
himself met with hybernating larvae of Ram escidenta and 
ReLobates fuscas, .which retained their perfect larval cha- 
racter. Hence it follows that, under certain conditions 
acting on the organism of these European larvae, their 
transformation into the terrestrial form of the animal does 
not take place. 
Not less strange is it that these creatures do not at once 
escape from their imprisonment in the water as soon as 
opportunity offers. Instead of climbing on the land at the 
first approach of spring, they prefer a longer sojourn in the 
water. Their nature seems no longer desirous of becoming 
terrestrial ; they hold fast their youthful form — a phenome^ 
non which Kollman has named “ Neotenism.” This faft is 
connected with the developmental phenomena of the 
axolotl. . This animal in Mexico very often declines to 
assume its land-guise, and it passes years, or even its entire 
life, in the form of a perennibranchiate. The remaining of 
a so highly developed vertebrate on a lower ontogenetic 
stage of . evolution is a fadt perfectly new to Biology, and is 
not less interesting than the extraordinary degree of adapta- 
bility among the Batrachians. 
In a memoir by Signor Camerano, recently published in 
the “Transactions of the Academy of Turin,” on the 
neotenism of the Amphibia, the author points out that 
Triton alpestris is particularly distinguished by the frequency 
with which it appears in the neotenic condition. According 
to a recent investigation not fewer than fifteen species ol' 
European Anoura may remain in the larval form longer than 
has been supposed. This is especially the case with Rana 
muta. The animals remain either entirely or partially in 
their aquatic stage. The organism can even carry certain 
of its youthful features over into its land-life. An entire 
