HEREDITY AND GERMINAL CONTINUITY 315 



to the development of particular parts of the embryo. The 

 removal of any one of these pre-localized areas prevents the 

 development of the part with which it is genetically related. 

 Researches of this kind, necessitating great ingenuity in 

 method and great talents in the observers, are widening the 

 field of observation upon the phenomena of heredity. 



The Inheritance of Acquired Characters. — The belief in 

 the inheritance of acquired characteristics was generally 

 accepted up to the middle of the nineteenth century, but the 

 reaction against it started by Galton and others has assumed 

 great proportions. Discussions in this line have been carried 

 on extensively, and frequently in the spirit of great partizan- 

 ship. These discussions cluster very much about the name 

 and the work of Weismann, the man who has consistently 

 stood against the idea of the inheritance of acquired charac- 

 ters. More in reference to this phase of the question is given 

 in the chapter dealing with Weismann's theory of evolution 

 (see p. 398). Wherever the truth may lie, the discussions 

 regarding the inheritance of acquired characteristics pro- 

 voked by Weismann's theoretical considerations, have re- 

 sulted in stimulating experiment and research, and have, 

 therefore, been beneficial to the advance of science. 



The Application of Experimental and Statistical Methods 

 to the Study of Heredity. Mendel. — The earliest experi- 

 mental investigations of heredity were conducted with plants, 

 and the first epoch-making results were those of Gregor Men- 

 del (182 2-1884) (Fig. 95), a monk, and later abbot, of an 

 Augustinian monastery at Brunn, Austria. In the garden 

 of the monastery, for eight years before publishing his re- 

 sults, he made experiments on the inheritance of individual 

 (or unit) characters in twenty-two varieties of garden peas. 

 Selecting certain constant and obvious characters, as color 

 and form of seeds, length of stem, etc., he proceeded to cross 

 these pure races, thus producing hybrids, and, thereafter, 



