32 
IOWA ACADEMY OP SCIENCES. 
ORIGIN AND SIGNIFICANCE OP SEX. 
BY C. C. NUTTING. 
This paper is not presented as a contribution to our knowl- 
edge of the subject of the origin of sex, so much as an attempt 
to express concisely a theory of sex drawn from, various sources, 
but principally from a work on the ‘‘Evolution of Sex” by 
Geddes & Thomson, a work which seems to me to mark an 
epoch in the science of philosophical biology. 
My excuse for presenting this subject before you to-night 
lies in the fact that it has been my fortune within the past year 
to personally investigate the origin of the sex-elements in one 
group of animals, the hy droids, and to follow in the footsteps 
of that great master August Weismann, whose studies have 
given such an impetus to the search for truth in the realm of 
sex and heredity. 
My own studies have resulted in a conviction that there is 
truth in the theory advanced by Geddes & Thomson, and my 
effort this evening will be to state this theory, in a slightly 
modified form, in a series of definite propositions, each one of 
which I believe to be defensible, if not invulnerable. 
First, however, it will be necessary to call to your minds the 
most important facts concerning reproduction among the one- 
celled animals, or Protozoa, 
The simplest form of reproduction is that of the amoeba, in 
which there is a simple division of the body mass of the parent 
cell into two portions, each of which becomes an independent 
organism. This is known as the process of reproduction by 
fission. 
Turning xo a somewhat higher group of Protozoa we find 
another step introduced in the reproductive process. If we 
study the Paramecium, for instance, we will find that it multi- 
plies by fission, as does the amoeba, but that at intervals 
