CHAP. XIX.] 
THE MADAGASCAR GROUP. 
403 
varies greatly in colour in the different islands, so that he could 
always tell from which particular island a specimen had been 
brought. This is analogous to the curious fact of certain lizards 
on the small islands in the Mediterranean being always very 
different in colour from those of the mainland, usually becoming 
rich blue or black (see Nature, Yol. XIX. p. 97) ; and we thus 
learn how readily in some cases differences of colour are brought 
about by local conditions. 
Snakes, as is usually the case in small or remote islands, are 
far less numerous than lizards, only two species being known. 
One, Dromicus seychellensis , is a peculiar species of the family 
Colubridse, the rest of the genus being found in Madagascar and 
South America. The other, Boodon geometricus, one of the 
Lycodontidse, or fanged ground-snakes, inhabits also South and 
West Africa. So far, then, as the reptiles are concerned, there is 
nothing but what is easily explicable by what we know of the 
general means of distribution of these animals. 
We now come to the Amphibia, which are represented in the 
Seychelles by two tailless and two serpent-like forms. The frogs 
are, Rana mascariensis, found also in Mauritius, Bourbon, An- 
gola, and Abyssinia, and probably all over tropical Africa ; and 
Megalixalus infrarufus, a tree-frog altogether peculiar to the 
islands, and forming a peculiar genus of the widespread tropical 
family Polypedatidse. It is found, Dr. Wright informs me, on 
the Pandani or screw-pines ; and as these form a very character- 
istic portion of the vegetation of the Mascarene Islands, all 
the species being peculiar and confined each to a single island 
or small group, we may perhaps consider it as a relic of the 
indigenous fauna of that more extensive land of which the 
O 
present islands are the remains. 
The serpentine Amphibia are represented by two species of 
Ceecilia. These creatures externally resemble large worms, 
except that they have a true head with jaws and rudimentary 
eyes, while internally they have of course a true vertebrate 
skeleton. They live underground, burrowing by means of the 
ring-like folds of the skin which simulate the jointed segments 
of a worm’s body, and when caught they exude a viscid slime. 
The young have external gills which are afterwards replaced by 
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