SEPTENARY AND OTHER SYSTEMS. 993 
racy. The question is not, how many apparent divi- 
sions can be made? but does each division, by itself, 
form a circular group? If not, they cannot be natural. 
If such writers would only recollect the admission which 
they set out with, that every natural group is a circle, 
*“they would not so often flounder about in all the 
difficulties which necessarily attend the supposition of 
two determinate numbers.” * 
(273.) Mr. MacLeay makes the following sound ob- 
servations regarding septenary theories; and they are 
equally applicable to any determinate number which spe- 
culative ideas may give rise to. ‘ The number seven 
might also, perhaps, for obvious reasons, occur tothe mind, 
were it allowable in natural history to ground any rea- 
soning except upon facts of organisation. The idea 
of this number is, however, immediately laid aside, on 
endeavouring to discover seven primary divisions of 
equal degree in the animal kingdom. It is easy, indeed, 
to imagine the prevalence of a number ; the difficulty 
is to prove it. The naturalist, therefore, requires 
something more than the statement of a number, before 
he allows either a preconceived opinion, or any analogy 
-not founded on organic structure, to have an influence 
on his favourite science. He requires its application to 
nature, and its illustration by facts.” T 
* MacLeay’s Letter to Dr. Fleming, p. 33. 
+ Linn, Trans. vol. xiv. p. 57. note. 
