82 THE PERPETUATION OF LIVING BEINGS, 



a little bulb, or portion of the plant, detaches itself, 

 drops off, and becomes capable of growing as a separate 

 thing. That is the case with many bulbous plants, 

 which throw off in this way secondary bulbs, which 

 are lodged in the ground and become developed into 

 plants. This is an asexual process, and from it results 

 the repetition or reproduction of the form of the ori- 

 ginal being from which the bulb proceeds. 



Among animals the same thing takes place. Among 

 the lower forms of animal life, the infusorial animal- 

 culse we have already spoken of throw off certain por- 

 tions, or break themselves up in various directions, 

 sometimes transversely or sometimes longitudinally ; 

 or they may give off buds, w T hich detach themselves 

 and develop into their proper forms. There is the 

 common fresh-water Polype, for instance, which multi- 

 plies itself in this way. Just in the same way as the 

 gardener is able to multiply and reproduce the pecu- 

 liarities and characters of particular plants by means 

 of cuttings, so can the physiological experimentalist, 

 — as was shown by the Abbe Trembley many years 

 ago, — so can he do the same thing with many of the 

 lower forms of animal life. M. de Trembley showed 

 that you could take a polype and cut it into two, or 

 four, or many pieces, mutilating it in all directions, 

 and the pieces would still grow up and reproduce com- 

 pletely the original form of the animal. These are all 

 cases of asexual multiplication, and there are other in- 

 stances, and still more extraordinary ones, in which 

 this process takes place naturally, in a more hidden, a 

 more recondite kind of way. You are all of you fa- 

 miliar with those little green insects, the Aphis or 

 blight, as it is called. These little animals, during 



