LECTURE IV. 



THE PERPETUATION OF LIVING BEINGS, 

 HEREDITARY TRANSMISSION AND 

 VARIATION. 



The inquiry which we undertook, at our last meet- 

 ing, into the state of our knowledge of the causes of the 

 phenomena of organic nature, — of the past and of the 

 present, — resolved itself into two subsidiary inquiries : 

 the first was, whether we know anything, either his- 

 torically or experimentally, of the mode of origin 

 of living beings; the second subsidiary inquiry was, 

 whether, granting the origin, we know anything about 

 the perpetuation and modifications of the forms of 

 organic beings. The reply which I had to give to 

 the first question was altogether negative, and the 

 chief result of my last lecture was, that, neither his- 

 torically nor experimentally, do we at present know 

 anything whatsoever about the origin of living forms. 

 We saw that, historically, we are not likely to know 

 anything about it, although we may perhaps learn 

 something experimentally ; but that at present we are 

 an enormous distance from the goal I indicated. 



I now, then, take up the next question, What do we 



