312 NATURAL SCIENCE [November 
its original qualities; even where the transmission is alternate, we 
may admit that the different conditions at the different stages of a 
genetic cycle modify the organisms produced. In the simplest case 
of collateral transmission, as presented by Volvoxz globator, the steril- — 
ised colonial cells so closely resemble more primitive independent 
forms in their behaviour and character, that we may well believe 
that they have inherited these from such forms, directly and un- 
altered, from some Protist ancestor, while the reproductive cells have 
become modified. But it is impossible to suggest such an explana- 
tion for the higher Animals and Plants, since a nerve-cell with its 
outgrowths many feet long, or a woody fibre which has expended all 
its living protoplasm in the building up of a firm wall, can only have 
been evolved as portions of a highly-specialised colonial organism. 
The difficulty of explaining the mechanism of collateral trans- 
mission in Metazoa and Metaphytes by the direct transmission in 
Protista has been the origin of the recent lively discussions on 
heredity. To biologists saturated with the implicit conviction that 
only direct cellular transmission was alone possible, some mysterious 
agency, that should be contained in the reproductive cells, and be 
handed down by them in their direct cellular descent, was an 
essential assumption ; and this agency is supphed by Weismann in 
his Germ-Plasm Theory. ‘The reader will do well to bear in mind 
that it has been presented to the world in successive editions; each 
has been greeted as final by the disciples, who have made light of 
the objections raised thereto, though on every occasion such objec- 
tions induced the Master to recast the theory in his next work. 
Our presentment of the theory upheld in the “Germ Plasm; A 
Theory of Heredity,” published in London. in 1893, may therefore, 
for aught anyone can tell, become obsolete very shortly, owing to 
the author's “ having (to use his own phrase) in the meantime gained 
a deeper insight.” 
Weismann conceives that in the nucleus of what we have 
termed ‘reproductive’ (and also, in part, ‘embryonic’) cells is a 
mixed plasm, the ‘germ-plasm, composed of certain entities, the 
‘determinants’ for the several organs of the colony; that when the 
cell divides at the limit of growth into two similar cells, the germ- 
plasm and the several determinants divide in the same way, so that 
the determinants are the same in each of the daughter-cells as they 
were in the parent. But in those divisions which give rise to 
specialised cells the germ-plasm divides as a whole, in such a way 
that the determinants are only distributed between the daughter- 
cells, some to one, some to another: we may say that there is 
distribution or repartition, not the true division of the several 
determinants. Similarly, the determinants each contain a group of 
minor entities the biophors, and in the ultimate divisions of the cells 
