HO VICTOR E. SHELFORD 
3 The relation of physiological characters to geographic range. . 596 
a Laws governing the reactions of animals.............. 597 
by Law? of mimimumtys..755 152 ho eno ot eee 597 
c Law of toleration of physical factors..--............5- 598 
4. ~"Fentative laws of distribution’. .a.% 22204 ie eee oek one 600 
De Clagsiticanionvolsenvaronmmlentses: ee et eee 600 
1 Elementary principles:ef classification...... 2.5.5. 4..24.... 5 601 
2 The best index of geographic complexes..................... 601 
Hache animal tormeationssse anaes oe ene ae ee ee eee 602 
(Classification ofetormstiOnsae seer eran anne 603 
AM Erinciplesmote <classiicatiOne ss hae eta eee 603 
b The geographic formations of the world.............. 604 
IV The problems, methods and relations of physiological animal geography. 607 
ASIP To blemish: asc pee ot ie tec ee ee Ghat eis Rae Ee ee ae 607 
fl PAB chad Or vere cr ee etre ead utc re net ete Ue) TC ACT Ean 607 
2) EP STONO LYLE tele ee ee ented oe nae eet ee 608 
Be MMleth ods thts ..r tees Rie paraa ree Nate? 29S ree ah pd eg ee 609 
CG Relations tocounem cub jecusermres cre yest re ttt 0 cee en eee ee 609 
ID) ehechuture: brol@giygrascccer ce crt ecm ae eter iceas ole pntie ee tans eee 611 
Vi General <suimimary ss 0 oe crit eee oe ee ee rete ee ee ee 612 
Acknowled omiemtsi (eyo )sass 2 aero eT Tee ot 8 613 
Bilbliggrapliyiwes.p-eire eats voeke sche nae EEE Rec hoi. oe ae eee 615 
I.’ INEFRODUCTION 
Only a working knowledge of the facts of animal geography 
is necessary for the recognition of at least two or three lines for 
the development of investigation, and for organization into a 
science. Likewise, a casual inspection of the existing liter- 
ature, indicates clearly that only one or at most two of the pos- 
sible lines of investigation have received attention; facts have 
been accumulated very largely from the point of view of animal 
structure, and organization has been based on evolution. Physi- 
ological lines have been proportionately neglected. It is our 
purpose to point out some of the possibilities of investigation 
and organization along physiological lines.! 
‘ When my paper on the life-histories and larval habits of the tiger beetles (’08) 
was prepared, it was my intention to follow it a year later with one on their ecology 
and distribution. While attempting to prepare this, it became evident that many 
of our so-called principles of distribution and some of the méthods employed in 
its study, were not wholly trustworthy as a basis for generalization. Before inter-' 
preting the beetle data, further observation and the examination of the existing ~ 
literature seemed advisable. We present here a point of view which developed 
in connection with this uncompleted task. 
