OTHER THEORIES OF SPECIES-FORMING 265 
WEISMANN’S THEORY OF GERMINAL SELECTION 
This theory was intended to rehabilitate the selection principle 
which had lost a great deal of prestige because of the serious character 
of the objections that had been raised against it, most of which have 
been stated in the last chapter. The theory is believed by its author 
to overcome all objections and doubts and to clear away all difficulties. 
“Its strength,” says Plate, “shall avail in four directions. First, it 
shall explain how not only degeneration (physiological) but rudimenta- 
tion (morphological) occurs in panmixia; second, why exactly those 
variations needed for the development of a certain adaptation appear 
at the right time; third, how correlation of adaptation comes to exist; 
and fourth, how variations are able to develop orthogenetically along 
a definite line without depending on the necessity of a personal selec- 
tion raising them step by step.” 
The essential feature of germinal selection, as the name implies, 
is a transfer of the struggle for existence to the germ cell. The germ 
cell is assumed to be a greatly reduced and simplified sample of the 
characters of the whole organism. Each independently variable part 
of the organism is supposed to be represented in the germ cell by a 
minute physiological unit, unique in composition and capable of 
reproducing the part in question ina neworganism. ‘These hereditary 
units are called ‘‘determinants.”’ Thus there is a different kind of 
determinant for each muscle of the body, for each bone, or for each 
independently functioning blood vessel; but, since all red blood cor- 
puscles are alike, there would be only one determinant for all of them. 
These determinants have to grow, and in cell division, to divide so as to 
furnish to daughter germ cells all of the necessary determinants for a 
whole individual. In their process of growth and multiplication, 
which goes on very rapidly at certain periods in the germ-cell cycle, 
these determinants are in competition among themselves for the 
available food supply. Some may be more favorably placed than 
others or may be more active chemically than others. There will thus 
arise a struggle within the germ for a chance to grow and reproduce 
their kind, which, for these determinants, might be as bitter as would 
be the struggle in nature among the whole organisms that are in com- 
petition for a place in the world. A determinant favored, perhaps 
accidentally or possibly because of inherent activity, by a good food 
supply would wax stronger and grow faster and would, logically, pro- 
duce a larger and more effective part when that particular germ cell 
developed into an adult. Other germ cells that would be the offspring 
