THE HEREDITARY BASIS 13 
the germ cells, but the germ cells were held to receive their store 
of pangens from antecedent germ cells. The denial of the flow of 
pangens from the body to the germ cells did away with the means 
by which Darwin accounted for the transmission of acquired or 
somatogenic characters. De Vries did not hesitate to accept the 
logical consequence of his hypothesis although he dwelt compara- 
tively little on this feature of his doctrine. 
It is in the writings of Professor August Weismann that we 
find the opposition to Lamarckism taking the form of vigorous 
and sustained attacks. Weismann in his early essay On Heredity 
set forth a very simple and plausible theory of transmission in his 
doctrine of the continuity of the germ plasm. This conception 
had been put forth previously by several writers (Owen, Galton, 
His, Nussbaum, Jager, Rauber), but it did not attract much 
attention until expounded in the lucid and attractive essays of 
Weismann who made it the basis of a series of brilliant and elabo- 
rate speculations on the mechanism of hereditary transmission. 
Weismann taught that the germ plasm is a substance separate 
from the soma plasm which forms the organs of the body, and 
that it is in no way the product of the body, although it is carried 
and nourished by the body. Germ plasm is handed on relatively 
unchanged from one generation to the next, part of it being trans- 
formed into soma plasm which: differentiates in various ways 
during embryonic development, but another part of it remaining 
undifferentiated in the germ cells to form the starting point of the 
next generation. Some germ plasm is, therefore, handed on in a 
continuous stream through successive generations, the bodies 
of the parents acting as ‘‘trustees of the germ plasm.” It is the 
continuity of the germ plasm that affords the basis for heredity. 
Parent and offspring resemble each other not because the off- 
spring are, in any sense, the product of the parent’s body, but 
because both parent and offspring arise from a common substance, 
the germ plasm. Poulton has aptly said that Weismann’s theory 
makes the offspring the younger brothers and sisters of their 
parents. We might compare successive generations to a series 
of plants arising from an underground runner or root stalk. 
