88 Proceedings of the Royal Physical Society. 
does he discuss in great detail the resemblance between the Mollusc eye 
and the Vertebrate eye? His point is this, that we would be justified in 
ruling purely mechanistic theory out of court “if it could be proved that 
life may manufacture the hke apparatus, by unlike means, on divergent 
lines of evolution, and the strength of the proof would be proportional 
both to the divergency between the lines of evolution thus chosen, and to 
the complexity of the similar structures found in them.” Therefore he 
takes one interpretation after another of the resemblance between the 
Molluse eye and the Vertebrate eye, and finds them wanting. He gives 
Darwinism and Lamarckism and other isms their innings, but his bowling 
is very deadly. ‘‘How can accidental causes, occurring in accidental order, 
be supposed to have repeatedly come to the same result, the causes being 
infinitely numerous and the effect infinitely complicated?” Two eyes— 
a Molluse’s and a Vertebrate’s—with striking resemblances, how are they 
so much alike, while their histories have been so different ? how can any 
conventional biological theory interpret this production of a similar effect 
by two different accumulations of an enormous number of small causes ? 
His own answer is that the puzzling sameness is due to the fact that life 
is the continuation of one and the same impetus divided into divergent 
lines of evolution. There is “a universal vital impulsion,’ and it is this 
fundamental kinship that accounts for convergent organs in widely separated 
forms of life. It need hardly be pointed out that to show that previous 
explanations of the puzzle are wrong does not prove that Bergson’s 
explanation is right. 
THe Urce or Impetus or Evouurtion.., 
Evolution is racial transformation, and it does not always spell progress. 
It has its minuses as well as pluses, its parasites as well as pioneers, its 
hells as well as heavens. The tapeworm is as well adapted to its inglorious 
lot as the lark to heaven’s gate. But admitting all this, we stand face to 
face with the grand spectacle of the long ascent of life. Throughout the 
ages life has been slowly creeping upwards. And the question Why? has 
often been asked. More and more perfect adaptation we can understand, 
more and more thorough exploitation of the earth, the occupation of every 
niche, but why this insurgence, this climbing of precipitous heights? Why 
the big lifts in evolution? Why are we not all Mollusca ? 
To this question, M. Bergson addresses himself. “ Why has life gone on 
complicating itself, and, moreover, complicating itself more and more 
delicately and dangerously” —‘“Why, if there is not behind life an 
impulse, an immense impulse to climb higher and higher, to run greater 
