368 GEOGRAPHIC DISTRIBUTION OF LIFE IN NORTH AMERICA. 
and insects. Among mammals the tapirs, monkeys, armadillos, nasuas, 
pecearies, and opossums of Central America and Mexico are replaced 
to the northward by wood-rats, marmots, chipmunks, foxes, rabbits, 
short-tailed field-nice of several genera, shrews, wild-cats, lynxes, short- 
tailed poreupines, elk, moose, reindeer, sables, fishers, wolverines, lem- 
mings, musk oxen, and polar bears. 
The trogons, saw bills, parrots, cotingas, and other birds of tropical 
America give place in turn to the cardinals, blue grosbeaks, mocking 
birds, tufted tits, and gnat-catchers of the Southern States; the chewink, 
indigo bird, tanager, bluebird, and robin of the Middle and Northern 
States; the Canada jays, crossbills, white-throated sparrows, and hawk 
owls of the northern coniferous forests, and the ptarmigans, snowy owls, 
and snowflakes of the Arctic circles. ; 
HISTORIGAL SYNOPSIS OF FAUNAL AND FLORAL DIVISONS PROPOSED 
FOR NORTH AMERICA. 
The recognition of the above-mentioned facts early led to attempts 
to divide the surtace of the iand into faunal and floral regions or zones, 
and no less than fifty-six authors have proposed such divisions for 
North America. Of these, thirty-one were zodlogists and twenty-five 
botanists. Of the zodlogists ten aimed to show the distribution of 
animals in general, eight of birds, four of terrestrial mollusks, three of 
mammals, one of reptiles and batrachians, and four of insects. Of the 
botanists, twenty-two aimed to show the distribution of plants in 
general and three of forest trees. . 
Of the writers who attempted to indicate the life areas of the New 
World prior to 1850, 68 per cent were botanists, while during the next 
twenty years (1850-1870), 65 per cent were zodlogists. This striking 
oscillation of the biological pendulum, first toward botany and then 
toward zodlogy, may be attributed in part at least to the influence of 
two great minds—Humboldt and Agassiz. Humboldt laid the corner- 
stone of the philosophic study of plant geography in 1805. Stimulated 
by his example and writings, botanists led the way and were almost 
the only occupants of the field until the middle of the present century, 
when the influence of the elder Agassiz gained the ascendancy and 
the botanists were replaced by zodlogists, who have been in the lead 
ever since. : 
The accompanying table shows the various authors referred to, the 
dates of the earliest publication of their divisions, the branch of biology 
on which their conclusions were based, and states whether or not their 
articles were accompanied by maps. 
