142 NEREIS. 
CHAPTER V. 
NEREIS, SPIO, AND CONGENERA. 
Coup the Systema Nature be perfected, it is not improbable that, 
excepting by interruption from tribes now extinct, the transition to suc- 
cessive genera would be very gradually accomplished ; if not by insensible 
degrees, one might venture to predict that the last of one genus, and the 
first of another, would appear not far asunder ; that the distinctions pre- 
sented would be but inconsiderable, farther than in the features peculiar 
to each denoting their separation. 
I know that some distinguished philosophers have expressed a dif- 
ferent opinion, thinking each genus so distinct and independent of itself, 
as to be void of every bond of connection; that it has been so since the 
origin of things, and will so remain. 
Whether there be actually a connecting chain or not, it belongs to 
each observer diligently to record what he has seen, leaving it to some 
scientific systematist to arrange and combine all the knowledge which 
may be derived from the labour of others besides his own. 
In this way the precise state of information would be obtained, 
so that the purposes of creation might be conjectured, and whether cer- 
tain genera were allied or estranged. 
There is no single territory, even the most extensive on thesurface 
of the globe, from which more than a partial view, commonly one most 
limited, of some branch or other of animated nature, can be derived, 
