NO TRANSMUTATION OF SPECIES. 395 
of which Geology takes cognizance, of that 
systematic and uniform arrangement of the 
Animal Kingdom, under which every family is 
nearly connected with adjacent and cognate fa- 
milies. Three of the families under considera- 
tion are among the present inhabitants of the 
water, while the foiirlh has been long extinct, 
and occurs only in a fossil state. When we see 
the most ancient Trilobites thus placed in imme- 
diate contact with our living Crustaceans, we 
cannot but recognize them as forming part and 
parcel of one great system of Creation, connected 
through its whole extent by perfect unity of 
design, and sustained in its minutest parts by 
uninterrupted harmonies of organization. 
We have in the Trilobites an example of that 
peculiar, and, as it is sometimes called, rudi- 
mentary development of the organs of locomotion 
in the Class Crustaceans, whereby the legs are 
made subservient to the double functions of 
paddles and lungs. The advocate for the theory 
of the derivation of existing more perfect species, 
by successive changes from more simple ancient 
forms, might imagine that he sees in the Trilo- 
bite the extinct parent stock from vvhich, by a 
series of developments, consecutive forms of more 
perfect Crustaceans may, during the lapse of 
ages, have been derived ; but according to this 
hypothesis, we ought no longer to find the same 
simple condition as that of the Trilobite still 
