CONTENTS.

Introduction[165]
I. The Germ-Plasm[174]
1.Historical development of the theory as to the localization of the germ-plasm in the nucleus[174]
2.Nägeli’s ‘idioplasm’ is not identical with Weismann’s ‘germ-plasm’[180]
3.A retransformation of somatic idioplasm into germ-idioplasm does not take place[183]
4.Confirmation of the theory as to the significance of the nuclear substance afforded by Nussbaum’s and Gruber’s experiments on regeneration in Infusoria[185]
5.The nucleoplasm changes during ontogeny according to a certain law[186]
6.The identity of the daughter-nuclei produced by indirect nuclear division, as assumed by Strasburger, is not necessary for my theory[187]
7.The gradual decrease in complexity of the structure of the nucleus during ontogeny[190]
8.Nägeli’s view on the germs (‘Anlagen’) in the idioplasm[192]
9.The manner in which germ-cells arise from somatic cells[194]
10.’Embryonic’ cells in the mature organism[196]
11.The rule of probability is against a retransformation of somatic idioplasm into germ-plasm[198]
12.The regular cyclical development of the idioplasm founded upon phylogeny by Nägeli[199]
13.It follows from phyletic considerations that the germ-cells have not arisen at the end of ontogeny[201]
14.They originally arose at the beginning of ontogeny, but at a later period the time of their origin was displaced[202]
15.A continuity of the germ-cells does not now exist in most cases[205]
16.But there is a continuity of the germ-plasm[205]
17.Strasburger’s objection to my supposition that the germ-plasm passes along distinct routes[209]
18.The cell-body may remain unchanged when the nucleus is changed[210]
19.It is conceivable that all somatic nuclei may contain some germ-plasm[211]
II. The Significance of the Polar Bodies[212]
1.The egg-cell contains two kinds of idioplasm; germ-plasm and histogenetic nucleoplasm[213]
2.The expulsion of the polar bodies signifies the removal of the histogenetic nucleoplasm[214]
3.Other theories as to the significance of the polar bodies[214]
4.The modes of occurrence of polar bodies[217]
5.Their possible occurrence in male germ-cells[219]
6.There are two kinds of nucleoplasm in the male germ-cells[219]
7.Polar bodies in plants[222]
8.Morphological origin of polar bodies[223]
III. On the Nature of Parthenogenesis[225]
1.The phenomena exhibited in the maturation of the egg are identical in parthenogenetic and sexual development[225]
2.The difference between parthenogenetic and sexual cells must be of a quantitative nature[226]
3.The quantity of the germ-plasm determines development[227]
4.The expulsion of polar bodies depends upon the antagonism between germ-plasm and ovogenetic nucleoplasm[230]
5.Fertilization does not act dynamically[231]
6.An insufficient quantity of germ-plasm arrests development[232]
7.Relation of the nucleus to the cell[234]
8.The case of the bee does not constitute any objection to my theory[234]
9.Strasburger’s views upon parthenogenesis[237]
10.Parthenogenesis does not depend upon abundant nutrition[239]
11.The indirect causes of sexual and parthenogenetic reproduction[241]
12.The direct causes[242]
13.Explanation of the formation of nutritive cells[243]
14.Identity of the germ-plasm in male and female germ-cells[246]
Note[249]

IV.
THE CONTINUITY OF THE GERM-PLASM AS THE
FOUNDATION OF A THEORY OF HEREDITY.