{204} When I formed this idea, I was not aware of one which_Vestiges of the Natural History of Creation

faintly to foreshadow it—namely, Socrates’s doctrine, afterwards dilated

on by Plato, that “previous to the existence of the world, and beyond its

present limits, there existed certain archetypes, the embodiment (if we

may use such a word) of general ideas; and that these archetypes were

models, in imitation of which all particular beings were created.”

{208} The numbers 1, 3, 6, 10, 15, 21, 28, &c. are formed by adding the

successive terms of the series of natural numbers thus:

1 = 1

1+2 = 3

1+2+3 = 6

l+2+3+4 = 10, &c.

They are called triangular numbers, because a number of points

corresponding to any term can always be placed in the form of a triangle;

for instance—

. . . .

.. .. ..

... ...

....

1 3 6 10

{215} Kirby and Spence.

{221} See an article by Dr. Weissenborn, in the New Series of “Magazine

of Natural History,” vol. i. p. 574.

{224} “It is a fact of the highest interest and moment that as the brain

of every tribe of animals appears to pass, during its development, in

succession through the types of all those below it, so the brain of man

passes through the types of those of every tribe in the creation. It

represents, accordingly, before the second month of utero-gestation, that

of an avertebrated animal; at the second month, that of an osseous fish;

at the third, that of a turtle; at the fourth, that of a bird; at the

fifth, that of one of the rodentia; at the sixth, that of one of the

ruminantia; at the seventh, that of one of the digitigrada; at the

eighth, that of one of the quadrumana; till at length, at the ninth, it

compasses the brain of Man! It is hardly necessary to say, that all this

is only an approximation to the truth; since neither is the brain of all

osseous fishes, of all turtles, of all birds, nor of all the species of

any one of the above order of mammals, by any means precisely the same,

nor does the brain of the human fœtus at any time precisely resemble,

perhaps, that of any individual whatever among the lower animals.

Nevertheless, it may be said to represent, at each of the above-mentioned

periods, the aggregate, as it were, of the brains of each of the tribes

stated; consisting as it does, about the second month, chiefly of the

mesial parts of the cerebellum, the corpora quadrigemina, thalami optici,

rudiments of the hemispheres of the cerebrum and corpora striata; and

receiving in succession, at the third, the rudiments of the lobes of the

cerebrum; at the fourth, those of the fornix, corpus callosum, and septum

lucidum; at the fifth, the tubor annulare, and so forth; the posterior

lobes of the cerebrum increasing from before to behind, so as to cover

the thalami optici about the fourth month, the corpora quadrigemina about

the sixth, and the cerebellum about the seventh. This, then, is another

example of an increase in the complexity of an organ succeeding its

centralization; as if Nature, having first piled up her materials in one

spot, delighted afterwards to employ her abundance, not so much in

enlarging old parts as in forming new ones upon the old foundations, and

thus adding to the complexity of a fabric, the rudimental structure of

which is in all animals equally simple.”—_Fletcher’s Rudiments of

Physiology_.

{226} Project Gutenberg note: the table in the book is very wide. Since

it won’t fit within the normal Gutenberg margins, and cannot be

reproduced typographically, the rows of the table have been broken out as

follows.—DP.

Table shows: scale of animal kingdom (the numbers indicate orders); order

of animals in; ascending series of rocks; fœtal human brain resembles, in

(The numbers indicate orders)

Rocks: 1. Gneiss and Mica Slate system