It brought
morphologists face to face again with the wonderful diversity of organic
forms, with the unity of plan underlying that diversity, with the
admirable adjustment of organ to function and of both to the life of the
whole.

Milne-Edwards' theoretical views, as expounded in his _Introduction a la
zoologie generale_ (1851), well reflect this Cuvierian attitude.[305] He
acknowledges himself the debt he owes to Cuvier; "the further I advance
in the study of the sciences which he cultivated with so sure a hand,"
he writes in 1867, "the more I venerate him."

Milne-Edwards frankly takes up the teleological standpoint, and
interprets organic forms on the assumption that they are purposive and
rationally constructed. "To arrive at an understanding of the harmony of
the organic creation," he writes, "it seemed to me that it would be well
to accept the hypothesis that Nature has gone about her work as we would
do ourselves according to the light of our own intelligence, if it were
given us to produce a similar result. Comparing and studying living
things as if they were machines created by the industry of man, I have
tried to grasp the manner in which they might have been invented, and
the principles whose application would have led to the production of
such an assemblage of diversified instruments" (p. 435). The problem is
to discover the laws which rule the diversity of organic forms. The
first and most obvious of these laws is the "law of economy," or the law
of unity of type. Nature, as Cuvier pointed out, has not had recourse to
all the possible forms and combinations of organs; she appears to work
with a limited number of types and to get the greatest possible
diversity out of these by varying the proportions of the constitutive
materials of structure. Within the limits of each type Nature has
brought about diversity by raising her creatures to different degrees of
perfection. This is the second law of organic form, and it is this law
that Milne-Edwards chiefly elaborates. Degrees of perfection mean for
him, as for Aristotle, primarily degrees of perfection of function, but
since structure is necessarily in close relation with function,
perfection of function brings in its train increased perfection of
organisation. This can only be attained by a division of labour[306] among
the organs and by their consequent differentiation. An animal is like a
workshop where some complicated product is manufactured, and the orga