544 The American Naturalist. [July, 
cell is rather conservative and the male cell progressive; the 
union of these cells produces variability in the offspring, 
exhibited especially in the regions of the offspring correspond- 
ing to the regions of functional disturbance in the parent. 
This hypothesis was well considered, and while that feature 
of it which distinguishes the male and female germ-cells as 
different in kind has been disproved, and the whole concep- 
tion of gemmules is now abandoned, the fact still remains that 
we shall nevertheless be obliged to offer some hypothesis to 
explain the facts disregarded by Weismann for which Brooks 
provides in his theory of the causes of variation. 
2. Continuity of Germ-cells—The central idea here is an 
outgrowth of our more modern knowledge of embryogenesis 
and histogenesis, and is, therefore, comparatively recent; it is 
that of a fundamental distinction between the “ germ-cells,” 
as continuous and belonging to the race, and the “ body-cells,” 
as belonging to the individual. Weismann has refined and 
elaborated this idea, but it was not original with him. 
Richard Owen, in 1849, Haeckel, in 1866, Rauber; in 
1879, in turn dwelt upon the distinction which Dr. Jaeger, 
now of manufacturing fame, first clearly stated: 
“Through a great series of generations the germinal proto- 
plasm retains its specific properties, dividing in every repro- 
duction into an ontogenetic portion, out of which the individ- 
ual is built up, and a phylogenetic portion, which is reserved 
to form the reproductive material of the mature offspring. 
This reservation of the phylogenetic material I described as 
the continuity of the germ protoplasm. . . . Encapsuled 
in the ontogenetic material the phylogenetic protoplasm is 
sheltered from external influences, and retains its specific and 
embryonic characters.” The latter idea has, under Weismann, 
been expanded into the theory of isolation of the germ-cells. 
Galton introduced the term “stirp” to express the sum 
total of hereditary organic units contained in the fertilized 
ovum. His conception of heredity was derived from the 
1See Parthenogenesis, in his Anatomy of Vertebrates. 
Generelle Morphologie, vol. ii., p. 170. 
3Zool. Anz., vol. ix., p. 166. 
