93)
dissected all kinds of animals, from holothurians to whales. His
interest was, however, that of the physiologist, and he was not
specially interested in problems of form. It is interesting to note a
formulation in somewhat confused language of the recapitulation
theory. The passage occurs in his description of the drawings he made
to illustrate the development of the chick. It is quoted in full by
Owen (J. Hunter, _Observations on certain Parts of the Animal
OEconomy_, with Notes by Richard Owen. London, 1837. Preface, p.
xxvi). We give here the last and clearest sentence--"If we were to
take a series of animals from the more imperfect to the perfect, we
should probably find an imperfect animal corresponding with some stage
of the most perfect."

The tendency of the time was not towards morphology, but rather to
general natural history and to systematics, the latter under the
powerful influence of Linnaeus (1707-1778). The former tendency is
well represented by Reaumur (1683-1757) with his observations on
insects, the digestion of birds, the regeneration of the crayfish's
legs, and a hundred other matters. To this tendency belong also
Trembley's famous experiments on Hydra (1744), and Roesel von
Rosenhof's _Insektenbelustigungen_ (1746-1761).

Bonnet (1720-1793) deserves special mention here, since in his _Traite
d'Insectologie_ (1745), and more fully in his _Contemplation de la
Nature_ (1764), he gives the most complete expression to the idea of
the _Echelle des etres_.

This idea seems to have taken complete possession of his imagination.
He extends it to the universe. Every world has its own scale of
beings, and all the scales when joined together form but one, which
then contains all the possible orders of perfection. At the end of the
Preface to his _Traite_ _d'Insectologie_ (OEuvres, i., 1779) he
gives a long table, headed "Idee d'une Echelle des etres naturels,"
and rather resembling a ladder, on the rungs of which the following
names appear:--

MAN.
Orang-utan.
Ape.

QUADRUPEDS.
Flying squirrel.
Bat.
Ostrich.

BIRDS.
Aquatic birds.
Amphibious birds.
Flying Fish.

FISH.
Creeping fish.
Eels.
Water serpents.

SERPENTS.
Slugs.
Snails.

SHELL FISH.
Tube-worms.
Clothes-moths.

INSECTS.
Gall insects.
Taenia.
Polyps.
Sea Nettles.
Sensitive plant.

PLANTS.
Lichens.
Moulds.
Fungi, Agarics.
Truffles.
Corals, and Coralloids.
Lithophytes.
Asbestos.
Talcs, Gypsums.
Selenites, Sla