13 



Experiments of Herbst on larvae of sea-urchins. 

 The potassium larva. 

 The lithium larva. 



Reactions following mutilation. 



Healing. 



Regeneration of lost parts. 



Polarization. 



Heteromorphosis (Loeb, Woods Holl Lect. 



1893)- 

 Effects following removal of testes and ovaries. 



Comparison with effect of excision of thyroid 



gland. 



7. Heredity and Variation. 



i. General Co7isiderations. 



Meaning of heredity. 



Prevalence of variation. 



Distinction between racial and individual variation. 



Distinction between acquired and congenital varia- 

 tions. 



Importance of congenital variations as a measure of 

 heredity. 



Distinction between continuous and discontinuous 

 variation. Sports. 



Distinction between substantive, meristic, and ho- 

 mceotic variation. 



ii. Phenomena of Individual ]^ariatio7i. 



(Darwin, Animals and Plants under Domestication ; Darwin, 

 Descent of man; Galton, Natural Inheritance; Bateson, 

 Materials for the Study of Variation; Weismann, Studies in 

 the Theory of Descent; Weismann, Essays upon Heredity; 

 Ellis, Man and Woman.) 



