HEREDITY AND GERMINAL CONTINUITY 309 
matter around a nucleus, and the medical men prior to 1858 
believed in free cell-formation within a matrix of secreted 
or excreted substance. This doctrine was held with tenacity 
especially for pathological growths. Virchow demonstrated, 
however, that there is a continuity of living substance in all 
growths—that cells, both in health and in disease, arise only 
by the growth and division of previously existing living cells; 
and to express this truth he coined the formula “omnis 
cellula e cellula.’ Manifestly it was necessary to establish 
this law of cell-succession before any idea of germinal con- 
tinuity could prevail. Virchow’s work in this connection 
is of undying value. 
When applied to inheritance the idea of the continuity of 
living substance leads to making a distinction between germ- 
cells and body-cells. This had been done before the obser- 
vations of Virchow made their separation of great theoretical 
value. Richard Owen, in 1849, pointed out certain differ- 
ences between the body-cells and the germinal elements, 
but he did not follow up the distinction which he made. 
Haeckel’s General Morphology, published in 1866, forecasts 
the idea also, and in 1878 Jaeger made use of the phrase 
“continuity of the germ protoplasm.” Other suggestions 
and modifications led to the clear expression by Nussbaum, 
about 1875, that the germinal substance was continued by 
unbroken generations from the past, and is the particular 
substance in which all hereditary qualities are included. 
But the conception finds its fullest expression in the work 
of Weismann. 
Weismann’s explanation of heredity is at first sight 
relatively simple. In reply to the question, “Why is the 
offspring like the parent?” he says, ‘“ Because it is composed 
of some of the same stuff.” In other words, there has been 
unbroken germinal continuity between generations. His idea 
of germinal continuity, z.e., unbroken continuity, through all 
