46 
THE ORGANIC CELL 
produce an embryonic form in which, on the whole, both the 
characters of the germ-cells have an equal effect, it is to be 
concluded that the chromatin of the nucleus is the source of 
hereditary characters, while the position of the cytoplasm is 
merely that of a subordinate agent. 
Weismann’s Theory of Germinal Continuity. Homo 
nascitur, non fit. 
The older theories of heredity assumed that the germ-cells 
were made up of samples taken from every part of the body. 
This is the conception embodied in Darwin’s theory of Pan- 
genesis. These ultra-microscopical particles derived from all 
the cells of the individual were termed gemmules, and were 
supposed to circulate in the body, finally coming to rest 
in the germ-cells. By this theory Darwin sought to explain 
such phenomena as the regeneration of lost parts, the in- 
heritance of acquired characters (the Lamarckian factors), 
sexual and non-sexual reproduction, also reversion to a distant 
ancestor. 
The hypothesis (which Darwin himself described as only 
provisional) was one of the first in which an attempt was made 
to account for the above phenomena. It, however, never 
received much support, there being no evidence of the existence 
of gemmules, and the idea of so many millions of these particles 
finding a resting-place in the germ-cells was incomprehensible. 
Darwin’s theory, however, did one great service to the science 
of biology — it stimulated thought, and led to the development 
of other theories which finally culminated in Weismann’s 
celebrated doctrine of Germinal Continuity. 
The central conception of Weismann’s theory is that the 
germ-cells possess an independence of their own, that they 
are quite distinct from the body or somatic cells ; also that 
the germ-cells of one generation give rise, not only to the 
bodies of the next generation, but also to their contained 
germ-cells ; in other words, the body cannot produce germ- 
cells, but merely contains them. 
Weismann challenged the whole of the Lamarckian principle 
in the following words : ‘ I do not propose to treat of the whole 
