A. Nototropa.--Embryo bent upwards.

Ord. 3. Protura.--The tail is first formed. (Mysis.)

Ord. 3. Saccomorpha.--A maggot-like larva-skin is first formed.
(Isopoda.)

B. Gasterotropa.--Embryo bent ventrally.

Ord. 5. Zoeogona.--Full number of limbs not produced in the egg.
Zoea-brood. (The majority of the Podophthalmata.)

Ord. 6. Ametabola.--Full number of limbs produced in the egg. (Astacus,
Gecarcinus, Amphipoda less Hyperia ?)

This sample may suffice. The farther we go into details in this
direction, the more brilliantly, as may easily be imagined, does the
naturalness of such an arrangement as this force itself upon us.

All things considered, we may apply the judgment which Agassiz
pronounced upon Darwin's theory, with far greater justice to the
propositions just examined:--"No theory," says he, "however plausible it
may be, can be admitted in science, unless it is supported by facts."


CHAPTER 11. ON THE PROGRESS OF EVOLUTION.

From this scarcely unavoidable but unsatisfactory side-glance upon the
old school, which looks down with so great an air of superiority upon
Darwin's "intellectual dream" and the "giddy enthusiasm" of its friends,