154 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the physical constitution of the protoplasm, why is it inconceivable that 
this constitution should be, under certain circumstances and to a certain 
extent, so modified that the metabolic activity no longer follows its own 
orbit, but after more or fewer revolutions comes to a standstill and 
results in death ? Even if w'e cannot penetrate into the mysteries of the 
constitution of living matter, we may say that a rigorous and unceasing 
natural selection is unremittingly active in maintaining it at such an 
exact standard as to preserve its immortality, and every lapse from this 
standard is followed by death. 
From the instant that natural selection relaxed its watch on this 
quality of immortality, the process of panmixia, which led to its 
abolition, began. When once individuals arose among monoplastids, in 
the protoplasm of which occurred such variations in chemical and mole- 
cular constitution as to result in a gradual check on the metabolic cycle, 
it would happen that these individuals died ; a permanent variety could 
not grow out of such variations. But, if there arose among hetero- 
plastids individuals with a similar differentiation of the somatic cells, 
the death of these cells would not be detrimental to the species, since 
its continuance is insured by the immortal germ-cells. After the differen- 
tiation into germinal and somatic cells natural selection was, speaking 
metaphorieally, trained to bear on immortality in the germ-cells, but on 
quite other qualities in the somatic cells. 
The recent observations of Klein on Volvox show that as soon as the 
germ-cells are ripe and emerge from the spheres, the ciliated somatic 
cells begin to slirivel up, and die in one or two days. 
The immortality of living matter is not life without beginning or 
end, but life which, after its first commencement, can continue inde- 
finitely with or without modification ; it is a cyclical activity of organic 
material devoid of any intrinsic momentum which would lead to its 
cessation, just as the motion of the planets contains no intrinsic mo- 
mentum which would lead to its cessation, although it has had a com- 
mencement and will some day, through the operation of extrinsic forces, 
have an end. 
After pointing out the differences between “ ideal ” and “ real ” 
theories and tbe relation of his own theory to that of Darwin’s theory 
of pangenesis. Prof. Weismann explains that his essays represent a series 
of researches, and urges that an early must not be set against a later 
expression of opinion. He does not recognize Prof. Vines’ somato- 
plasm ; his own idiojdasm (or germ-plasm) of the first ontogenetic grade 
is not modified into the somatoplasm of Vines, but into idioplasm of 
the second, third, hundredth, &c., grade, and every one impresses its 
character on the cell containing it. 
Our author is distinctly opposed to the rejuvenescence theory ; he 
thinks we should not speak of the sexual elements as male and female, 
but as paternal and maternal ; there is no opposition of the one to the 
other, they are essentially alike, and differ only so far as one individual 
differs from another of the same species. Fertilization is merely a union 
of the hereditary tendencies of two individuals, tendencies which are 
bound up with the matter of the nuclear loops; the cell-body of the 
ovum and spermatozoon is indifferent in this connection, and plays 
merely the part of a nutritive matter w’hich is modified and shaped by 
