ACQUIRED CHARACTERS 45 



through internal secretions, give us grounds for believing that 

 an adequate basis will be found when our knowledge of the 

 organism becomes more complete. 



The problem of acquired characters, after all, concerns only 

 the higher animals. In the lower animals and in plants no 

 such sharp distinction exists between body and germ-cells 

 as we find in the higher animals. We may reproduce the 

 entire plant from a cutting of root, stem, or even a leaf in 

 some cases. Hence there is more chance in such cases of 

 direct modification of the cells capable of reproduction, for 

 most of the cells of the plant retain this capacity. In the 

 lowest organisms {protozoa, bacteria) there is no distinction 

 whatever between body and germ-cells. Every cell is capable 

 of reproduction; and modifications produced in a cell by the 

 environment are handed on directly to the next generation. 

 For example medical men have learned how to decrease the 

 virulence of diseases at will by heat or chemicals acting 

 directly on the disease germs. They are thus able to confer 

 immunity to a virulent disease by first producing and 

 then introducing into the body a feeble form of the same 

 disease. 



If in the lower organisms the potentialities of living sub- 

 stance can thus be altered, it seems reasonable to suppose 

 that the same possibility may exist in the higher animals and 

 plants, provided agencies capable of producing change are 

 allowed to act on the germinal substance. It is the sheltered 

 position of the germ-cells which seems ordinarily to exempt 

 them from direct modification, but we cannot safely assume 

 that they are in all cases free from such modification. Experi- 

 ments of Stockard show that in guinea-pigs repeatedly in- 

 toxicated with alcohol, the germ-cells are enfeebled so that 

 offspring of such parents, whether male or female, are more 

 likely to be feeble and sickly, and so to die. Experiments of 

 Hertwig show that similarly the germ-cells of frogs are 

 capable of being injured by emanations of radium in conse- 

 quence of which enfeebled or abnormal offspring may be 

 produced. 



