LECTUKE IV. 



TOE 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 in- 

 quiries : the first was, whether we know anything, 

 either historically 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 historically 

 nor experimentally, do we at present know anything 

 whatsoever about the origin of living forms. We saw 

 that, historically, we arc not likely to know anything 

 about it, although we may perhaps learn something ex- 

 perimentally ; 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 know of the reproduction, the perpetuation, and the 

 modifications of the forms of living beings, supposing 



