ASEXUAL REPRODUCTION. 



175 



CHAPTER XIV. 

 ASEXUAL REPRODUCTION. 



I. Artificial Division. — Weeping willows are by no means 

 scarce trees in Britain, yet as they never flower they must all have 

 grown from slips; or, in other words, artificial asexual multiplication. 

 So, too, only more naturally, the Canadian pondweed has spread 

 prodigiously in our lochs, canals, and rivers, never flowering, but 

 owing its increase wholly to the asexual process. Every one knows 

 how the gardener increases his stock by slips and cuttings, thus taking 

 advantage of the power a part has to reproduce the whole. Quite in 

 the same way, cultivators of bath-sponges bed out little fragments to 



Fig. 51. — A group of Sea-Anemones. — From Andres. 



keep up a convenient supply. In the last century, the Abbe Trembley 

 delighted himself and others by the often repeated observation that to 

 get many hydra polypes out of one, the simplest and quickest way 

 was to cut it in pieces. Though the fragment be very small, it will 

 reproduce the whole, provided always that it have to start with fair 

 samples of the different kinds of cells in the body. The 'same may be 

 done any day with the much larger sea-anemones. So the earth- 

 worm, curtailed by the spade, does not necessarily suffer loss, though 

 it suffer pain. The head-portion grows a new tail, and even a 

 decapitated portion may reproduce a head and brain, — not that this is 

 saying much for these. 



