1882.] The Difficulties in the Heredity Theory. 547 
chain from which the individuals are mere offshoots. Thus 
the germ-plasm of man is continuous with that of all ancestors, 
in his line of descent, and we have an explanation of the 
early stages observed in development in which the human 
embryo passes through a succession of metamorphoses resem- 
bling the adult forms of lower types. 
In order to emphasize, as it were, the passage of the germ- 
plasm from one generation to another without deterioration in 
its marvellous hereditary powers, Weismann added the idea 
of its isolation. Not only does he repudiate the pangenesis 
notion of increment of germ-plasm by addition of gemmules, 
but he believes that it is unaffected by any of the normal 
changes in the somatic or body-cells. As this continuity and 
isolation would render impossible the transmission of charac- 
ters acquired by the somatoplasm, Weismann began to examine 
the evidence for such transmission, and coming to the conclu- 
sion that it was insufficient, in his notable essay on “Heredity,” 
in 1883, he boldly attacked the whole Lamarckian theory and 
has continued to do so in all his subsequent essays. 
Being forced to explain evolution without this factor, he 
claimed that variation in the germ-plasm was constantly 
arising by the union of plasmata from different lines of 
descent in fertilization, and that these variations are constantly 
being acted upon by Natural Selection to produce new types. 
He thus revived Darwin’s earlier views of evolution, and this 
in part explains his strong support by English naturalists. 
It will be seen at once that there are a number of distinct 
questions involved. 
The matter of first importance in life is the repetition and 
preservation of type, the principle which insures the unerring 
accuracy and precision with which complex organs are built 
up from the germ-cells; the force of regression and the more 
remote forces of reversion all work in this conservative direc- 
tion; the theory of the preservation of these forces in a speci- 
fic and continous form of protoplasm is by far the most plausi- 
ble we can offer at present. The matter of second importance, 
but equally vital to the preservation of races, in the long run, 
is the formation of new types adapted to new circumstances of 
