286 ANIMAL BIOLOGY 



plex that this modification will be reproduced as such or in any 

 representative degree. However, it should be emphasized that 

 biologists in general recognize the potent influence of environment 

 and the organism's reactions to the environment on the destinies 

 of the race, even though they see, at present, no grounds for a 

 belief that any specific modification can enter the heritage and 

 so be reproduced. (Fig. 199.) 



In this connection the question of the inheritance of disease will 

 undoubtedly arise in the reader's mind. But this is really not a 

 special case. If the disease is the result of a defect in the germinal 

 constitution, it may be inherited just as any other character, 

 physiological or morphological, that has a germinal basis. But if 

 the disease is a disturbance set up in the body by some accident 

 of life or through infection by specific microorganisms, before birth 

 or later, it is a modification and inheritance does not occur. Of 

 course, the well known fact that susceptibility or immunity to 

 disease-producing organisms - - the ' soil ' for their development — 

 may be inherited is not an exception to this statement. It may, 

 however, be suggested in passing that from the standpoint of the in- 

 dividual born malformed, structurally or mentally, as a result of 

 parental alcoholism, syphilis, or other obliquities, it probably will 

 not appear of the first moment that the sins have been visited 

 otherwise than by actual inheritance. (Fig. 250.) 



The whole question of the non-herit ability of modifications, or 

 acquired characters, is a relatively new point of view which has 

 been fostered by the elusiveness of crucial experimental evidence, 

 by an ever-increasing knowledge of the details of the chromosome 

 mechanism of inheritance, and by the general influence of Weis- 

 mann's contrast of the soma and germ. Indeed, Lamarck did not 

 question the inheritance of acquired characters and made it the 

 corner-stone of his theory of evolution, while some have even 

 gone so far as to say that either there has been inheritance of 

 acquired characters, or there has been no evolution. However, 

 the question is not so serious as that, as will be seen later on; 

 though it obviously is profoundly important from many view- 

 points, biological, educational, and sociological. In passing, it 

 may be mentioned for those who would like to believe that ac- 

 quired characters are inherited, that if desirable modifications 

 were inheritable, undesirable ones would be also. Perhaps Nature 

 is merciful! (Figs. 305,309.) 



