6 BRITISH SERPENTS. 
animal types, the class Reptilia is one of absorbing 
interest. Standing, as it does, next to the amphibians 
on the one side and to the birds on the other, the 
reptiles show a distinct relationship to both; so that 
there is found in them a further development of a 
type of structure first seen in the amphibians, and 
at the same time indications of features which appear 
in greater perfection in the birds. So much so, indeed, 
is this the case that reptiles and birds have been 
classed together as a single series of animals under 
the one name Seuropsida. Thus we see that “no one 
class of vertebrates stands alone by itself. Every 
year fresh researches by paleontologists and the re- 
exanunation of living vertebrates, especially in their 
embryonic history, prove that no single class, not even 
a type so well circumscribed as the modern birds, is 
without links, forming genetic bonds, allying them 
all together. The different classes of vertebrates, as 
well as of other branches of the animal kingdom, 
form an ascending series.” ! 
In the class Reptilia we find some members which 
are equally at home in water or on land, or which 
spend part of their time in one element and another 
part on the other. Our own common ring snake, 
though a capital swimmer and fond of water, is 
mainly a land serpent; while our adder, as a rule, 
is averse to water, and is but rarely found at all in 
damp places. 
1 Packard. 
