Mode of Inheritance of Adaptive Characters. 71 



looks upon it as acting in accordance with the environment. 

 He does not put forward any mechanism that would account 

 for the suppression of certain characters and the retention of 

 others, but evidently considers the soma in adaptation to its 

 surroundings as indirectly affecting the germ cells, and in 

 some way producing survival of like qualities in them. 



Experiments have shown that the serum of blood of certain 

 animals has a specific chemical reaction in relation to the 

 blood of other animals (8), — the injection of the blood of 

 one animal into that of another, giving to the serum of the 

 latter new properties antagonistic to the blood cells of the 

 former. The immunity produced by infection in zymotic 

 diseases, and the whole system of antitoxin treatment, seem 

 to have bearings in the same direction, viz., the formation of 

 enzymes, or some chemical bodies, which are antagonistic 

 in their relation to one another. Eelated to this question 

 is the effect of commencing maturation of the germ cells in 

 producing secondary sexual characters, and the effect of 

 the thyroid gland upon the rest of the body. Castration 

 prevents the development of secondary sexual characters, 

 and removal of the thyroid gland has very marked effects. 

 In the latter case, that some enzyme or chemical body is the 

 active agent, seems to be shown by the results of administer- 

 ing the gland in the form of an extract for medicinal 

 purposes. Other glands of the body, such as the adrenal, 

 seem to have similar relations to the chemistry of the body, 

 and it seems probable, indeed, that all tissues form some 

 characteristic chemical bodies as a part of their metabolism, 

 which have further relations to the other tissues. In the 

 theory of pangenesis brought forward by Darwin to explain 

 the method of accumulation of acquired characters in the 

 germ cells, there has always been the difficulty of the orien- 

 tation of qualities brought from different parts of the body in 

 forming a morphological basis for heredity, and research has 

 further shown a greater and greater difficulty in accepting any 

 direct transmission of characters from the soma to the germ 

 cells. That positive characters can be directly passed from 

 the soma to the germ cell seems therefore out of court, but, 

 on the other hand, there is no possible reason that neo-ative 



