14 
THE OEGANIC CELL 
factors has raged a severe straggle. Darwin accepted the 
theory of their being inherited ; and, as an explanation of how T 
it was possible for the effects of use and disuse, &c., to be in- 
herited, he formulated his ingenious provisional hypothesis of 
pangenesis. This theory suggests that the germ-cells receive 
minute gemmules from every part of the body, and on this 
assumption explained the transmission of both inborn and 
acquired characters. This theory was the most speculative 
of all Darwin’s writings, and, though discarded, it must 
always remain of interest from the wonderful skill used in 
its construction. 
Brooks, in 1888, attempted to rejuvenate the theory of 
pangenesis. In the above year Professor A. Weismann startled 
the scientific world by issuing a sweeping challenge of the whole 
of the Lamarckian factors. 1 ‘ In my opinion this [the hereditary 
substance] can only be the substance of the germ-cells ; and 
this substance transfers its hereditary tendencies from genera- 
tion to generation, at first unchanged, and always uninfluenced 
in any corresponding manner by that which happens during 
the life of the individual which bears it. If these views be 
correct, all our ideas upon the transformation of species require 
thorough modification, for the whole principle of evolution by 
means of exercise (use and disuse) as professed by Lamarck, 
and accepted in some cases by Darwin, entirely collapses.’ 
Professor Weismann continues by stating the impossibility of 
the transmission of acquired traits, for it seems impossible to 
understand that changes in the body should affect the plasm 
of the germ cells so as to bring about corresponding changes in 
the offspring. 
Weismann asserts that not a single case of transmission 
of acquired characters will stand a rigid scrutiny. Inheritance 
does not take place from the body of the parent to that of 
the child. ‘ The child inherits from the parent germ cell, 
not from the parent-body which bears it,’ and the germ cell 
owes its characteristics not to the body which bears it, but to 
its descent from a pre-existing germ cell of the same kind. Thus 
the body is, as it were, an offshoot from the germ cell (see 
diagram). 
1 See Essays upon Heredity, vol. i., by A. Weismann (Clarendon Press, 
Oxford: 1891). 
