CANNIBAL TADPOLES 
These tadpoles are very carnivorous, and feed upon 
minute water crustaceans. The black tadpoles of the 
British puddle eats decaying vegetation, though on 
occasions it will become a pure cannibal. At the sides 
of the mouth of the Plaathande tadpole are a pair of 
very long feelers, which must be tactile, and when first 
described led the describer to place the animal as an 
adult creature in the neighbourhood of some of the 
Siluroid fishes, whose heads are beset with such ten- 
tacles. In the Xenopus tadpole the tentacle gets less 
and less important with advancing days, and finally 
remains in the adult as a small process under the eye, 
which can be recognised in the illustration. 
THE FRESH-WATER SIREN. 
Since the year 1876, when the first example was 
received, there have been always, or at any rate gene- 
rally, specimens of this newt-like and American creature 
in the Zoological Gardens. The siren (Siren lacertina), 
eel-like though it appears, belongs to the great group of 
the amphibia ; like the Japanese newt (Megalobatrachus), 
like the little English newt, and the axolotl it belongs 
to that division of the amphibia known as the Urodela, 
from the fact that they have tails, which the frogs and 
toads havenot. All these tailed Batrachia are inhabi- 
tants of the temperate regions, only just getting into 
South America, not reaching tropical Africa, and totally 
absent from Australia and its adjacent and heated 
islands. It is not indeed too much to say that they 
represent in cooler waters the tropical mud-fishes, Ceva- 
todus, Lepidosiven, and Protopterus. Where there are 
Dipnoi there are no tailed amphibians and vice-versa. 
As it is not unreasonable to trace the origin of the tailed 
amphibians, which are clearly the most primitive of 
existing amphibians, from some dipnoid form, these 
293 
