248 J. D. Dana—Cephalization a fundamental principle 
so often exhibited in a general way—as announced by Agassiz 
—between the biological succession and embryonic develop- 
ment. I need not dwell on the facts in this place, as they are 
well understood. 
Professor Marsh has recently brought forward facts which ex- 
emplify fully the view that the succession in the animal life of 
the globe has been -more or less connected with brain-progress, 
facts which sustain strongly the doctrine, which I have else 
where urged, that this progress involved changes in structures 
in obedience to the principle of cephalization.* 
Professor Marsh statest that in the Eocene Dinoceras, from the 
cky Mountain region, the brain was not more than one-eighth 
the bulk of that of the modern Rhinoceros—its nearest recent 
ally; in the Miocene Brontotherium it was much larger, about 
equalling that of the Indian Rhinoceros; and in a Pliocene 
e 
and olfactory lobes have even diminished in size; ; 
“there is some evidence that the same general law of ‘a 
growth holds good for birds and reptiles from the Cretace? 
to the present time.” sci 
A growth of eight fold in bulk since the early be aioe 
enormous, vastly exceeding in amount the growth od nat 
organs; in fact, the species related to the arsenite od. 
. 
—_ 
* Author’s Manual of Geology, 1874, p. 596. 
+ This Journal, III, viii, 66, 1874, and xi, 163, with figures peed 496, with 
brain; xi, 335, with figures of the brain in Brontotherium; an 
Cs) i C 
} e Coryp : 
Thid., xi, 425, 1876. Thid., xii, 61, July, 1876. |. icor portion 
: "jaws are in some pated; relatively short through te Tr grad The 
being imperfectly developed, and this condition is a mark of tts Pree 
this deg Hid the normal Post™ 
oS 
» 
; Se ee ee as 4 
of the posterior molar—an abbreviation which reaches 
ey ee 
