296 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
in that body are not identical now becomes obvious. For in such 
cases as those just cited one sees the germinal substance which is to 
carry on the race set aside at an early period in a given individual; it 
takes no part in the formation of that individual’s body, but remains 
a slumbering mass of potentialities which must bide its time to awaken 
into expression in a subsequent generation. Thus an egg does not 
develop into a body which in turn makes new germ-cells, but body and 
germ-cells are established at the same time, the body harboring and 
nourishing the germ-cells, but not generating them. The same must 
be true also in many cases where the earliest history of the germ-cells 
cannot be visibly followed, because in any event, in all higher animals, 
they appear long before the embryo is mature and must therefore be 
descendants of the original egg-cell and not of the functioning tissues 
of the mature individual. This need not necessarily mean that the 
germ-cells have remained wholly unmodified or that they continue 
uninfluenced by the conditions which prevail in the body, especially 
in the nutritive blood and lymph stream, although as a matter of fact 
_ most biologists are extremely skeptical as to the probability that 
influences from the body beyond such general indefinite effects as 
might result from under-nutrition or from poisons carried in the blood, 
modify the intrinsic nature of the germinal substances to any measur- 
able extent. 
Germinal continuity.—The germ-cells are collectively termed the 
germinal protoplasm and it is obvious that as long as any race continues 
to exist, although successive individuals die, some germinal protoplasm 
is handed on from generation to generation without interruption. 
This is known as the theory of germinal continuity. When the organ- 
ism is ready to reproduce its kind the germ-cells awaken to activity, 
usually undergoing a period of multiplication to form more germ-cells 
before finally passing through a process of what is known as matura- 
tion, which makes them ready for fertilization. The maturation 
process proper, which consists typically of two rapidly succeeding 
divisions, is preceded by a marked growth in size of the individual cells. 
Individuality of chromosomes.—Before we can understand fully 
the significance of the changes which go on during maturation we shall 
have to know more about the conditions which prevail among the 
chromosomes of cells. As already noted each kind of animal or plant 
has its own characteristic number and types of chromosomes when 
these appear for division by mitosis. In many organisms the chromo- 
somes are so nearly of one size as to make it difficult or impossible to 
