THE PERPETUATION OF LIVING BEINGS, 

 HEREDITARY TRANSMISSION AND 

 VARIATION 



THE inquiry which we undertook, at our last meeting, 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 historically or experi- 

 mentally, 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 any- 

 thing 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 

 know of the reproduction, the perpetuation, and the 

 modifications of the forms of living beings, supposing that 

 we have put the question as to their origination on one 

 side, and have assumed that at present the causes of their 

 origination are beyond us, and that we know nothing 

 about them ? Upon this question the state of our know- 

 ledge is extremely different ; it is exceedingly large, and, 

 if not complete, our experience is certainly most extensive. 

 It would be impossible to lay it all before you, and the 

 most I can do, or need do to-night, is to take up the 

 principal points and put them before you with such promin- 

 ence as may subserve the purposes of our present argument. 



The method of the perpetuation of organic beings is of 

 two kinds, the asexual and the sexual. In the first the 

 perpetuation takes place from and by a particular act of 

 an individual organism, which sometimes may not be 



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