CONTENTS xiii 



PAGE 



external conditions for expression. Nature of individual 

 response. Possibility of chromosomal modification. Use 

 and disuse in chromosomes. Somatic and germinal 

 chromosomes. Continuity of germ plasm. Modifications 

 and the internal environment. Modifications and pre- 

 adaptation. Reversibility. Conditions for experiment. 



Index • • • • ^29 



