292 Recent Progress and present State of Systematic Botany. 
we had hitherto formed no conception. The last of the emi- 
nent observers of nature who persistently maintained the inde- 
pendent creation and absolute fixity of species (the late distin- 
guished Professor Agassiz) has recently gone from among us; 
and it may now be given as a generally received doctrine, that 
all natural methods must be founded on affinities as dependent 
on consanguinity. Fifteen years have sufficed to establish a 
theory, of which the principal points, in as far as they affect 
systematic botany, may be shortly stated as follows :— 
“That although the whole of the numerous offspring of an 
individual plant resemble their parent in all main points, there 
are slight zndividual differences between them. 
“That among the few who survive for further propagation, 
the great majority, under ordinary circumstances, are those 
which most resemble their parent, and thus the species is con- 
tinued without material variation. 
‘That there are, however, occasions when certain individuals 
with slightly diverging characters may survive and reproduce 
races in which these divergences are continued even with in- 
creased intensity, thus producing Varieties. ; 
“That in the course of an indefinite number of generations 
ants of the common parent, have become extinct. 
“That these species have in their turn become the parents of 
‘groups of species, i.e., ’ 3, , of a higher and 
higher grade according to the remoteness of the common par- 
ent, and more or less marked according to the extinction or 
preservation of unaltered primary or less altered intermediate 
orms. 
“ As there is thus no difference but in degree between a 
variety and a species, between a species and a genus, between 
a genus and order, all disputes as to the precise grade to which 
a group really belongs are vain. It is left in a great measure 
to the judgment of the systematist, with reference as much to 
the use to be made of his method as to the actual state of 
things, how far he should go in dividing and subdividing, and 
to which of the grades of division and subdivision he shall 
give the names of Orders, Su ers, Tribes, Genera, Sub- 
