242 LAMARCK, HIS LIFE AND WORK 
to speak of the existence of a linear and regular series 
of species or even genera: such a series does not 
exist. But I speak of a quite regularly graduated 
series in the principal groups, z.¢., in the principal 
system of organizations known, which give rise to 
classes and to great families, series most assuredly 
existing both among animals and plants, although 
in the consideration of genera, and especially in that 
of species, it offers many lateral ramifications whose 
extremities are truly isolated points. 
“‘ However, although there has been denied, in a 
very modern work, the existence in the animal king- 
dom of a'single series, natural and at the same time 
graduated, in the composition of the organization of 
beings which it comprehends, series in truth neces- 
sarily formed of groups subordinated to each other 
as regards structure and not of isolated species or 
genera, I ask where is the well-informed naturalist 
who would now present a different order in the ar- 
rangement of the twelve classes of the animal king- 
dom of which I have just given an account? 
“T have already stated what I think of this view, 
which has seemed sublime to some moderns, and _ in- 
dorsed by Professor Hermann.” 
Each distinct group or mass of forms has, he says, 
its peculiar system of essential organs, but each organ 
considered by itself does not follow as regular a course 
in its degradations (modifications). 
“Indeed, the least important organs, or those least 
essential to life, are not always in relation to each 
other in their improvement or their degradation ; and 
an organ which in one species is atrophied may be 
very perfect in another. These irregular variations 
in the perfecting and in the degradation of non-essen- 
tial organs are due to the fact that these organs are 
oftener than the others submitted to the influences 
