176 
WEISMANN S THEORY OF GERM-PLASM. 
Aug., 1890. 
this will not necessarily be an effect in any way resembling its 
cause. Mr. Spencer says, that to assert that a re-organisation 
of any part of an organism has no effect upon its offspring, 
is to deny the “Persistence of Force;” but I cannot quite' 
see how this follows, as the re-organisation may have its due 
effect in many other ways besides that of reproducing its 
image in the offspring. 
Other important theories have been advanced by Stras- 
burger, Naegeli, and W. K. Brooks, of Baltimore, but it is 
not here necessary to discuss them, as I do not wish to treat 
of theories of heredity in general, but of the “ continuity of 
the germ-plasm,” according to Weismann in particular. 
Among the Protozoa, such animals as the familiar Amoeba 
multiply by fission; that is, when they have arrived at the 
limit of their size they simply divide into two, so that the 
resulting animals are identical in size, structure, and pro¬ 
perties. Of neither can it be said “ This is the mother,” or 
“ This is the daughter,” for both are just as old and in every 
wav the counternart of the other. If one were twice the 
*> 
size of its fellow, yet the fact of the similarity of age would 
invalidate the claim of the larger to be the mother. Being 
also the two halves of the original Protozoan, they are the 
same age as it was. This being the case, it follows, startling 
as the statement may seem, that every organism that has 
arisen by fission is as old as any of its predecessors, and in 
fact is as old as life itself. This will serve as an analogy to 
the “ continuity of the germ-plasm ;” still it is more than an 
analogy, it is the homologue of the process. 
Guided by this, Weismann supposes that the nuclear 
substance—the essential part of the germ-cell—is passed on 
without alteration of quality, though of course increasing 
in quantity, from the parent organism to the offspring, where 
it reproduces its inherited structure. During the building 
up of the body, all (or some) of the germ-plasm is preserved, 
and is concentrated in the reproductive glands, where it is 
increased by nourishment, and then passed on to the next 
generation, still the same as when received from the 
original source, but with the addition of any variation that 
may have taken place in its own substance. I speak of 
variation in the sense of the so-called “ spontaneous 
variation,” as contrasted with variation through the influence 
of the environment. 
The precise idea is difficult to express. In his lecture 
at Oxford, and subsequent paper in this magazine, Mr. 
Poulton used a diagram that makes the question a little 
more comprehensible, yet I do not think it advisable to adopt 
