EVIDENCE FROM EXPERIMENT 157 



All of these experiments, and many more that 

 might be cited, would seem to prove that it is pos- 

 sible to effect lasting and hereditary modifications in 

 animals by abrupt changes in their environment, and 

 the same result has been obtained with plants. By 

 injecting various substances into the young seed- 

 capsule, when the germs are becoming ready for fer- 

 tilization by the pollen, MacDougal effected some 

 very remarkable changes, which were hereditary 

 through four or more generations and remained sta- 

 ble, the plants exhibiting no tendency to return to 

 the parent type. Gager also produced hereditary 

 modifications in plants by exposing the seed-capsule 

 before fertilization to the action of radium, but these 

 results are not yet conclusive. 



Thus, the experimental proof goes to show that the 

 species of animals and plants are not fixed and 

 immutable entities, but are capable of extensive 

 modification even in the short time which is at the 

 command of the experimenter. 



In the first lecture it was stated that the experi- 

 ments of the Austrian monk, Johann Gregor Mendel, 

 published in 1866, had attracted no attention, because 

 they were too far ahead of their time and their far- 

 reaching significance was not perceived. Redis- 

 covered in 1900, Mendel's results have been enor- 

 mously extended and have led to the development of 

 the new science of Genetics. This is an extremely 

 complex subject, which would require more than one 

 course of lectures for its elucidation, not merely the 



