6 ON THE LAW WHICH HAS REGULATED 
the subject :—1st. The system of natural affinities. 
Qnd. The distribution of animals and plants in 
space. 8rd. The same in time, including all the 
phenomena of representative groups, and _ those 
which Professor Forbes supposed to manifest polar- 
ity. 4th. The phenomena of rudimentary organs. 
We will briefly endeavour to show its bearing upon 
each of these. 
The Form of a true system of Classification determined 
by this Law. 
If the law above enunciated be true, it follows that 
the natural series of affinities will also represent the 
order in which the several species came into exist- 
ence, each one. having had for its immediate anti- 
type a closely allied species existing at the time of 
its origin. It is evidently possible that two or three 
distinct species may have had a common antitype, 
and that each of these may again have become the 
antitypes from which ‘other closely allied species were 
created. The effect of this would be, that so long as 
each species has had but one new species formed on 
its model, the line of affinities will be simple, and 
may be represented by placing the several species in 
direct succession in a straight line. But if two or 
more species have been independently formed on the 
plan of a common antitype, then the series of affini- 
ties will be compound, and can only be represented 
‘by a forked or many branched line. Now, all at- 
tempts at a Natural classification and arrangement 
