PLESIOSAURUS. 213 
creation ; we have seen in proceeding through 
our examination of its details, that these appa- 
rent anomalies consist only in the diversified 
arrangement, and varied proportion, of parts 
fundamentally the same as those that occur in 
the most perfectly formed creatures of the pre- 
sent world. 
Pursuing the analogies of construction, that 
connect the existing inhabitants of the earth 
with those extinct genera and species which 
preceded the creation of our race, we find an 
unbroken chain of affinities pervading the entire 
series of organized beings, and connecting all 
past and present forms of animal existence by 
close and harmonious ties. Even our own 
bodies, and some of their most important organs, 
are brought into close and direct comparison 
wdth those of reptiles, which, at first sight, ap- 
pear the most monstrous productions of crea- 
tion; and in the very hand and fingers with 
which we write their history, we recognise the 
type of the paddles of the Ichthyosaurus and 
Plesiosaurus. 
Extending a similar comparison through the 
four great classes of vertebral animals, we find 
in each species a varied adaptation of ana- 
logous parts, to the different circumstances and 
conditions in which it was intended to be 
placed. Ascending from the lower orders, we 
trace a gradual advancement in structure and 
office, till we arrive at those whose functions 
