"Je dus donc, et cette obligation me prit un temps considérable,
je dus faire marcher de front l'anatomie et la zoologie, les
dissections et le classement; chercher dans mes premières
remarques sur l'organisation des distributions meilleures; m'en
servir pour arriver à des remarques nouvelles; employer encore ces
remarques à perfectionner les distributions; faire sortir enfin de
cette fécondation mutuelle des deux sciences, l'une par l'autre,
un système zoologique propre à servir d'introducteur et de guide
dans le champ de l'anatomie, et un corps de doctrine anatomique
propre à servir de développement et d'explication au système
zoologique."

It is deeply to be lamented that so many naturalists have entirely
overlooked this significant advice of Cuvier's, to combine zoölogical and
anatomical studies in order to arrive at a clearer perception of the true
affinities among animals. To sum it up in one word, he tells us that the
secret of his method is "comparison,"--ever comparing and comparing
throughout the enormous range of his knowledge of the organization of
animals, and founding upon the differences as well as the similarities
those broad generalizations under which he has included all animal
structures. And this method, so prolific in his hands, has also a lesson
for us all. In this country there is a growing interest in the study of
Nature; but while there exist hundreds of elementary works illustrating
the native animals of Europe, there are few such books here to satisfy the
demand for information respecting the animals of our land and water. We
are thus forced to turn more and more to our own investigations and less
to authority; and the true method of obtaining independent knowledge is
this very method of Cuvier's,--comparison.

Let us make the most common application of it to natural objects. Suppose