The Progress of the 
[Odtober, 
466 
declares, “ at least a presumption that he came into exist- 
ence at a much later date and by a much more rapid process 
of development. In that case it will be a fair argument 
that just as he is in his mental and moral nature, his capa- 
cities and aspirations, so infinitely raised above the brutes, 
so his origin is due in part to distinct and higher agencies 
than such as have affedted their development.” 
But is it necessary that the process of Evolution, by 
whatsoever agencies effected, must always have maintained 
a uniform degree of speed ? We have no desire to recur to 
“ catastrophism,” geological or biological, or to represent 
unknown and immeasurable forces as being arbitrarily in- 
troduced into adtion and again as arbitrarily withdrawn. 
But we find in phenomena governed by forces stridtly 
natural, and even measurable, changes occurring more 
rapidly at certain stages than at others. To take a simple 
and familiar instance, the progressive increase of the length 
of the day in spring and its corresponding decrease in 
autumn is much more rapid at the equinox than at any other 
time. Or, turning to a region much more closely connedted 
with the subjedt in hand, if we observe the development of 
an individual man — or indeed of any other animal — from 
birth to maturity, we do not find equal amounts of progress 
effedted in equal successive portions of time. We know 
that in the life of a youth there is a period when, in stature 
and in the development of his mental and bodily powers, he 
appears almost at a standstill for two or three years, this 
lull being followed by a period of intensified growth, in 
which he shoots up at once into manhood. Is it not at least 
possible that a similar want of uniformity may be traceable 
in the evolution of species ? Prof. Leconte argues that 
every organism will oppose a certain amount of resistance 
to agencies calculated to effedt a change. This resistance 
being once overcome, change will be for a time rapid, until 
a state of approximate equilibrium is again reached. Hence 
we may expedt that at certain points where a great change 
has taken place certain “ links ” — the intermediate forms — ■ 
will be missing. Their career is likely to be exceedingly 
short, not running to many generations, and for the same 
reason the number of individuals must be limited. Hence 
the probability of the fossil remains of such “ links ” being 
preserved for our inspedtion is infinitesimal indeed. When, 
on the other hand, the equilibrium is re-established, species 
exist with little change for centuries, possibly for thousands 
of years ; they spread over every accessible land suitable to 
their requirements, and increase in numbers as far as the 
