252 
ORIGIN OF LIFE IN AMERICA 
islands. Dr. Gadow next proceeds to argue that because one 
of these coecilians inhabits eastern Mexico, its ancestors must 
have travelled slowly across the whole neck of Central America 
since the close of the Miocene Epoch, when he assumes the 
isthmus to have been first opened up for southern immigrants. 
This argument is in so far faulty, as the coecilians need not 
necessarily have passed through Central America. The inti¬ 
mate relationship that exists among many ancient species of 
Central America to those of northern South America suggests 
the existence of some far older link between these countries. 
In very remote times species were, I believe, able to reach 
certain areas such as Guatemala and western Mexico long 
before the present Central America had come into existence, 
that is to say long before Pliocene times. Dr. Gadow himself 
urged that the Isthmus of Panama is but the last vestige of a 
former much broader land connection between North and 
South America (p. 243). In my opinion this should read 
“ the Isthmus of Panama contains some vestiges of a former 
much broader land connection.” 
To the uninitiated the Typhlopidae would seem nearly 
related to the coecilians. Both are snake-like burrowing crea¬ 
tures, and yet the former are true snakes and, therefore, 
reptiles, while the others are merely limbless amphibians. On 
close examination the true burrowing-snakes (Typhlopidae) 
are found to he covered with minute cycloid scales, and to 
exhibit other reptilian characters. Their distribution is ex¬ 
tremely discontinuous and extensive, and they are largely 
confined to solitary islands. That they possess no special 
facilities for accidental dispersal across the ocean is evident, 
and yet it is held by some zoologists that their presence on 
islands, such as Christmas island for instance, can only be 
due to such a cause. At any rate, the family exhibits all the 
signs of antiquity, and, in the absence of any positive evidence 
of accidentally distributed species, I am firmly convinced that 
they spread by the usual method of slow migration on land. 
Dr. Sarasin * places the dispersal of the family into pre- 
Cretaceous times, in spite of the fact that we possess no 
palaeontological evidence of their antiquity. All the same he 
* Sarasin, F., “ Tierwelt von Ceylon,” p. To. 
