584 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



assuming that, following these various procedures, a transformation took 

 place in the specific structure of the organismal differentials, but there is 

 evidence for the conclusion that the transplantations altered the cells to such 

 an extent that (1) phenotypic changes occurred, perhaps of a cytoplasmic 

 nature, which insured a greater resistance to the injurious effects of certain 

 hosts, or (2) the growth energy of the cells was increased, or (3) the pro- 

 duction and the diffusion of the organismal differentials of the grafts were 

 quantitatively diminished, or (4) the transplants were modified in such a 

 way that their reaction towards other individuals or species were altered by 

 means of secondary mechanisms without any actual change taking place in 

 the character of their organismal differentials. 



5. If we include in our analysis not only the tissues of higher organisms, 

 but also primitive, unicellular organisms, we find further analogies to the 

 above mentioned phenomena. It is known that in protozoa, changes in the 

 resistance to injurious chemicals as well as to high temperatures can be 

 produced, and that these may be transmitted to successive generations ; like- 

 wise, apparently spontaneous variations occur in these organisms and extreme 

 types of this kind can be selectively propagated. Especially striking are the 

 experiments in which parasitic protozoa, such as trypanosomes, were made 

 resistant to immune sera, to drugs, in particular, also to certain dyes, acting 

 specifically on these organisms. These adaptive changes can be observed in 

 vivo as well as in vitro. Likewise, in free-living protozoa, for instance in 

 paramaecia, new biotypes can be produced, which may differ structurally as 

 well as physiologically from the original type. Effects of this kind are 

 associated with chemical changes such as the antigenic constitution in 

 trypanosomes, as indicated by the acquired power of the organism to trans- 

 form a poisonous form of a chemical into a less poisonous one. These effects 

 may be transmitted by heredity to many asexual generations; but they seem 

 to be lost ultimately, especially under conditions of sudden changes in the 

 genetic constitution, such as those taking place at the time of conjugation or 

 endomixis. Whether these persistent modifications (Dauermodifikationen of 

 Jollos) are due to true gene mutations and therefore comparable to real 

 changes in organismal differentials, or whether they are due to cytoplasmic 

 alterations from which a return to the old equilibrium would take place 

 in the course of time is not certain. 



There is, therefore, in all these changes the question involved as to their 

 permanence and also as to the respective role of cytoplasm and genes in 

 their causation. However that may be we are directly concerned with such 

 induced modifications or mutations only in so far as they affect the relations 

 of different races and species to one another. 



6. In this connection we must also again refer to the experiments of 

 Reynolds, who succeeded in modifying the reactions of various protozoan 

 organisms towards each other by adding to the culture media in which they 

 were kept, fluids from culture media in which other organisms of the same 

 type had previously multiplied. In this way he could change the behavior 

 of pseudopodia belonging to different individuals and thus alter a reaction 



