306 Strasburger . — The Periodic Reduction of 
granules previously distributed in the linin-network, but also, 
and perhaps to the largest extent, the linin-network itself. 
For it is well known that the staining capacity of the contents 
of the nucleus increases considerably in the prophase, passing 
over for the most part into that readily stainable condition 
which we regard as an increase of the chromatin ; in the 
anaphase the nuclear contents undergo precisely contrary 
changes. In support of the view that the individual segments 
present in the chromosomes of nuclei about to divide, possess 
all the hereditary characteristics of the species and are, in 
fact, the true ids, may be adduced the results of the micro- 
scopic vivisection of unicellular organisms 1 : it has been 
found, namely, that a fragment of such an organism will 
regenerate itself to a complete individual if only it contains 
a portion of the nucleus. Again, I have observed that when, 
as not infrequently happens during the division of the pollen- 
mother-cells of Hemerocallis fulva , single chromosomes do 
not enter into the structure of either of the daughter-nuclei, 
but remain behind in the equatorial plane of the nuclear 
spindle, small pollen-grains are formed in relation with them. 
The small chromosome marks itself off from its surroundings, 
and a proportionate mass of the cytoplasm of the mother-cell 
is assigned to it 2 . The often very small pollen-grain develops 
quite normally and shows all the peculiarities of structure 
characteristic of the species. 
The serially arranged ids in the chromosome are, in my 
opinion, repetitions of each other, for no difference can be 
detected between them by actual observation. It is possible 
to go on to assume that they are repetitions which correspond 
to successive generations, and that they actually represent, 
as Weismann puts it, ancestral plasm. It is by their simul- 
taneous activity that the constancy of the species is pro- 
portionately maintained : for the co-operation of so many ids 
1 See especially A. Gruber, Mikroskopische Vivisection. Ber. d. naturf. Ges. in 
Freiburg im Br., Bd. VII, Heft I. 
2 Ueb. den Theilungsvorgang der Zellkerne, 1882, p. 20, and Taf. II, 
Figs. 63-65. 
