HEREDITY AND GERMINAL CONTINUITY = a2r1 
investigators reached their conclusions independently, al- 
though there is great similarity between them. Although the 
credit for the first formulation of the law of germinal con- 
tinuity does not belong to Weismann, that of the greatest 
claboration of it does. This doctrine of germinal continuity 
is now so firmly embedded in biological ideas of inheritance 
and the evolution of animal life that we may say it has become 
the corer-stone of modern biology. 
The conclusion reached—that the hereditary substance is 
the germ-plasm—is merely preliminary; the question remains, 
Is the germ-plasm homogeneous and endowed equally in all 
parts with a mixture of hereditary qualities? This leads 
to the second step. 
The More Precise Investigation of the Material Basis of 
Inheritance.—-The application of the microscope to critical 
studies of the structure of the germ-plasm has brought 
important results which merge with the development of the 
idea of germinal continuity. Can we by actual observation 
determine the particular part of the protoplasmic substance 
that carries the hereditary qualities? The earlest answer 
to this question was that the protoplasm, being the living 
substance, was the bearcr of heredity. But close analysis 
of the behavior of the nucleus during development led, 
about 1875, to the idea that the hereditary qualities are located 
within the nucleus of the cell. 
This idea, promulgated by Fol, Koelliker, and Oskar 
Hertwig, narrowed the attention of students of heredity 
from the general protoplasmic contents of the cell to the 
nucleus. Later investigations show that this restriction was, 
in a measure, right. The nucleus takes an active part 
during . cell-division, and it was very natural to reach the 
conclusion that it is the particular bearer of hereditary 
substance. But, in 1883, Van Beneden and Boveri made 
the discovery that within the nucleus are certain dis- 
