SOME NEW DOO s: 
THE GERM-PLasmM: A Theory of Heredity. By August Weismann. Translated 
by W. Newton Parker, Ph.D., and Harriet Ronnfeldt, B.Sc. Contemporary 
Science Series. Pp. 477. With 24 illustrations. London: Walter Scott, 1893. 
Price 6s. 
THE new volume of Professor Weismann, of which the translation is 
before us, departs from the historical method in which we have 
received his work. This is a deliberate presentation of his theory, 
incorporating, expanding, and explaining the ideas which have been 
shaped in his various essays. At the same time, it contains a number 
of novel hypotheses subsidiary to the theory, but necessary to it. It 
is not too little to say that the book is an excessively hard nut to 
crack, and that many will declare the kernel bitter who have not 
bitten through the epicarp. 
Speaking generally, this expanded account is a closer and more 
detailed theory of the structure and mechanism of the germ-plasm, 
bringing it closer into relation with, on the one hand, recent advances 
in actual observation of the structures and changes in the nucleus 
connected with cell-division, and on the other, with the observed 
details of inheritance, variation, asexual reproduction and _ re- 
generation of tissues. 
As before, the doctrine of the continuity of the germ-plasm is 
firmly insisted on, and it may be said that this, of all parts of Professor 
Weismann’s theory, has been subjected to the least successful criti- 
cism, and has received the most startling corroboration. This germ- 
plasma Weismann identifies with the chromatin fibril in the nucleus 
of egg-cells and sperm-cells. Before fertilisation, the nuclear fibril 
breaks up into a series of loops which Weismann calls idants. In 
ordinary sexual eggs the number of idants is twice halved, and by 
what Weismann calls these two reducing divisions the polar bodies 
are extended. It will be remembered that, originally, the first polar 
body was considered by Weismann to serve for the extrusion of that 
part of the nuclear matter which, having served to guide the 
maturation of the ovum, became useless when the ovum was mature. 
In his completed doctrine, he finds in the two polar bodies of normal 
sexual cells, and in the single polar body of parthenogenetic ova, a 
mechanism for reducing the bulk of germ-plasm—part of the apparatus 
for phylogenetic variation. The actual nuclear matter which controlled 
the maturation of the ovum he supposes to have passed into the 
protoplasm of the ovum, and, therefore, to be out of the reckoning 
when the behaviour of the nucleus is being interpreted. 
When the nuclear loops or idants are closely examined they 
exhibit a series of lumps or divisions as if they were built up of 
separate pieces like draught counters strung together. These sepa- 
