TRANSLATOR'S INTRODUCTION ix 



called biophores, which eventually pass into the 

 protoplasm of the cells in which they come to lie 

 and direct the vital activities of these cells. A 

 most important part of the theory is what it 

 supposes to occur during the embryological develop- 

 ment of the individual. The mass of germplasm 

 derived from the germplasm of the parent lies in a 

 mass of ordinary protoplasm. Both the protoplasm 

 and the germplasm, by the assimilation of food, 

 gradually increase in bulk until the adult size of 

 the organism is reached. Along with the increase 

 of size there occurs a gradual specialisation, during 

 which the tissues, organs, and structure of the 

 creature are attained. The simplest conception of 

 this process is to regard the initial mass as a single 

 cell, the nucleus of which is composed of the 

 parental germplasm. The nucleus and the proto- 

 plasm increase in size, and then, first the nucleus 

 and next the protoplasm divide, so that there are 

 formed two cells, each with a nucleus. Each of 

 these again divides, and the process goes on con- 

 tinuously, the new-formed cells gradually being 

 marshalled into their places to form the adult 

 tissues and organs, and they gradually assume the 

 special characters of these tissues and organs. 

 Now, Weismann's theory supposes that the first 

 division of the germplasm is what is called in 

 this translation a doubling division (Erbgleiche 

 Theilung). The mass has grown in bulk, without 

 altering its character, so that each resulting mass 

 is precisely like the other. One of the two portions 

 subsequently increases in bulk, and may again 



