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2888-89.] Mr J. A. Thomson on Theory of Heredity. 
In the second place, it is needful to notice at the outset Galton’s 
term “ stirp,” which he uses to express the sum total of the germs, 
gemmules, or organic units of some kind, which are to he found in 
the newly-fertilised ovum. 
(1) Only some of the germs within the stirp attain development 
in the cells of the “ body.” It is the dominant germs 
which so develop. 
(2) The residual germs and their progeny form the sexual 
elements or buds. The part of the stirp developed into the 
“ body ” is almost sterile. The continuity is kept up by the 
undeveloped residual portion. 
(3) The direct descent is not between body and body, but 
between stirp and stirp. “ The stirp of the child may be 
considered to have descended directly from a part of the 
stirps of each of its parents, but then the personal structure 
of the child is no more than an imperfect representation of 
his own stirp, and the personal structure of each of the 
parents is no more than an imperfect representation of each 
of their own stirps.” 
Here it will be seen that there is a very definite expression of the 
notion that the germinal cells of the offspring are in very direct 
continuity with those of the parents. The antithesis between the 
“ soma ” and the chain of sex-cells is emphasised. 
The history must also include Nussbaum, who called emphatic 
attention to the very early differentiation and isolation of the sex- 
elements to be observed in some cases. The theory both of J’ager and 
of Nussbaum is that of a continuity of germinal cells. The theory 
of Weismann is more strictly that of the continuity of germinal 
protoplasm. The position of Jager and Nussbaum may first be 
summarised more definitely: — 
(1) At an early stage in the embryo, the future reproductive 
cells of the organism are distinguishable from those which 
are forming the body. 
(2) The latter develop in manifold variety, and lose almost all 
likeness to the mother germ. 
(3) The former — the reproductive rudiments — are not implicated 
in the differentiation of the “soma,” remain virtually un- 
changed, continue the protoplasmic tradition unaltered. 
