with a vitellus, germinal vesicle and germinal spot" (paragraph 278).
"The organs of the body are formed in the sequence of their organic
importance; the most essential always appear first. Thus the organs of
vegetative life, the intestine, etc., appear later than those of animal
life, the nervous system, skeleton, etc., and these in turn are preceded
by the more general phenomena belonging to the animal as such"
(paragraph 318). "Thus, in Fishes, the first changes consist in the
segmentation of the vitellus and the formation of a germ, processes
which are common to all classes of animals. Then the dorsal furrow,
characteristic of the Vertebrate, appears--the brain, the organs of the
senses; at a later period are formed the intestine, the limbs, and the
permanent form of the respiratory organs, from which the class is
recognised with certainty. It is only after exclusion that the
peculiarities of the structure of the teeth and fins indicate the genus
and species" (paragraph 319). "Hence the embryos of different animals
resemble each other the more, the younger they are" (paragraph 320).
"Consequently the high importance of developmental history is
indubitable. For, if the formation of the organs takes place in the
order corresponding to their importance, this sequence must of itself be
a criterion of their comparative value in classification. The
peculiarities which appear earlier should be considered of higher value
than those which appear subsequently" (paragraph 321). "A system, in
order to be true and natural, must agree with the sequence of the organs
in the development of the embryo" (paragraph 322).

I do not know whether any one at the present day will be inclined to
subscribe to this proposition in its whole extent.* (* Agassiz' own
views have lately become essentially different, so far as can be made
out from Rud. Wagner's notice of his 'Essay on Classification.' Agassiz
himself does not attempt any criticism of the above cited older views,