104 



WHAT IS LIFE 



Tubularia 



Planaria 



storative powers of the triton organisation in a 

 most remarkable manner. 



The examples of this kind amongst inverte- 

 brates are legion and one or two may be mentioned 

 here. 



Observers of the common objects of the sea- 

 shore can scarcely have failed to have seen speci- 

 mens of the creature called tubularia. It has a 

 stem, the base of which is embedded in the sand 

 and a head-end surrounded by a ring of tentacles 

 and provided with a sort of proboscis. Almost 

 anything can be done with this creature in the 

 way of regeneration. If the head be snipped off 

 the base will grow a new head and the head a new 

 base, just as a worm chopped in two will do. If 

 instead of cutting it the animal be pulled up by 

 the roots and replanted head downwards the head- 

 end develops roots and the root-end becomes a 

 head with tentacles and proboscis. 



Finally, if we snip off the head and tail of the 

 polyp and hang it up in the water by a thread, it 

 will grow a head from either end. 



Another creature planaria, a parasitic worm, 

 can be cut up into a number of pieces all of which 

 will develop into complete individuals. Moreover 

 like the hydra it can be partially bisected and will 

 then grow into a kind of two-headed Nightingale 

 amongst planarians, with a single body and two 



