AMERICAN 
JOURNAL OF SCIENCE AND ARTS. 
[THIRD SERIES.]} 
ArT. XLII. oe and Succession of Vertebrate Life in 
tea ; a 0. C. Mars 
[Address before the American Associa tion for the Advancement of Science, at 
Nashville, Tenn., August 30, 1877.] 
Tue origin of life, and the order of —- in which its 
as forms have appeared upon the earth, offer to science 
most inviting and most difficult. field of research. 
Macech the primal origin of life is unknown, and may per 
haps never be known, yet no one has a right to say how ranch 
of the mystery now surrounding it science cannot remove. 
’ It is certainly within the domain of science to determine when 
the earth was first fitted to receive life, and in what form the 
earliest life began. To trace that life in its manifold changes 
through past ages to the present is a more difficult task, but _ 
one from which modern science does not shrink. In this wide 
field, every earnest effort will meet some degree of success ; 
every year will add new and important facts; and eve ry 
generation will bring to light some law, in — with 
which ancient life has been changed into life we see it 
around us to-day. That such a development noe taken pee 
no one will doubt who has carefully traced any single group 
of animals through its past history, as recorded in the ne of 
the earth. The evidence will be especially conclusive, if the 
group selected belongs to the higher forms of life, which tha 
sensitive to every change in their surroundings. “But lam 
TI need offer here no argument for — since to doabe 
Am. Jour. Sct. prea pee Vou. XIV, No. 83.—Nov., 
