THE PEKPETUATION OF LIVING BEINGS. 81 



that we Lave 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 Ave know 

 nothing about them ? Upon this question the state of 

 our knowledge 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 prominence as may subserve the pur- 

 poses 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 par- 

 ticular act of an individual organism, which sometimes 

 may not be classed as belonging to any sex at all. In 

 the second case, it is in consequence of the mutual ac- 

 tion and interaction of certain portions of the organisms 

 of usually two distinct individuals, — the male and the 

 female. The cases of asexual perpetuation are by no 

 means so common as the cases of sexual perpetuation ; 

 and they are by no means so common in the animal as 

 in the vegetable world. You are all probably familiar 

 with the fact, as a matter of experience, that you can 

 propagate plants by means of what are called " cut- 

 tings ; " for example, that by taking a cutting from a 

 geranium plant, and rearing it properly, by supply- 

 ing it with light and warmth and nourishment from 

 the earth, it grows up and takes the form of its parent, 

 having all the properties and peculiarities of the ori- 

 ginal plant. 



Sometimes this process, which the gardener per- 

 forms artificially, takes place naturally ; that is to say, 

 4* 



