152 The Science of Life. 



mann, is the germ-plasm, i.e. a special portion of the 

 nuclei of the reproductive cells, which, with great mor- 

 phological stability, keeps itself intact, and is sooner 

 or later re-established in the reproductive cells of the 

 growing organism. Nageli finds sufficient explanation 

 of the constancy of inheritance in the individuality and 

 persistence of what he calls the " idioplasm ". 



Kolliker, O. Hertwig, Strasburger, and Bambeke 

 may be noted for the emphasis which they have laid 

 upon the nuclei as transmitting or rather continuing the 

 essential characteristics from generation to generation. 

 Thanks to the researches of such investigators as Van 

 Beneden and Boveri, it is now certain that the male and 

 female nuclei contribute an equal share in forming the 

 segmentation-nucleus of the ovum. Nay more, each of 

 the first two daughter-cells has in its nucleus half of the 

 male and half of the female nuclear elements, and it is 

 possible that this marvellously exact dualism holds true 

 later on. 



Most daringly, perhaps, has the continuity been ex- 

 pressed by several, e.g. Berthold, Gautier, and Geddes, 

 in chemical terms. In a paper by the last-mentioned 

 on "Growth, Sex, Reproduction, and Heredity", the 

 following weighty sentence occurs: "If the repro- 

 ductive elements start with a specific protoplasm con- 

 tinuous with that of the combined mother ovum and 

 fertilizing sperm that is, with a concentrated accumu- 

 lation of characteristic anastates and katastates the 

 simple fact that the products of protoplasmic change 

 must be fixed, definite, and continuous, as in all chemi- 

 cal processes, gives us at once a protoplasmic basis 

 from which to explain the constant and necessary sym- 

 metry of segmentation and development". The views 

 of Berthold are closely similar. Inheritance is possible 

 only on the basis of the fundamental fact that in the 

 chemical processes of the organism "the same sub- 

 stances and mixtures of substances are reproduced in 

 quantity and quality with regular periodicity ". Gautier 

 discusses both variation and heredity from a chemical 

 point of view. " The force which maintains the species, 

 and gives it the character of constancy and resistance, 



