THE SIMPLEST LIVING THINGS 199 



is killed by alcohol, picric acid, or other preservative 

 solutions, and then stained ; and it shows a curious 

 breaking-up of its substance into thread-like fibres when 

 the animalcule is about to divide into two as is seen 

 also in all cells when the regular process of division of one 

 cell into two commences. The larger animalcules have 

 enabled us to find out what are the special properties of 

 the nucleus of cells, as contrasted with those of the rest 

 of the protoplasm. The trumpet animalcule (Stentor) 

 is a single cell, and though only one-thirtieth of an inch 

 long, is large enough to be cut into pieces by very skilful 

 use of a fine blade. It is found that, if we cut the 

 Stentor into four or five bits, all continue to " live " ; that 

 is to say, to swim about by the vibration of the hair-like 

 cilia on their surface. But those bits which have no 

 part of the nucleus in them die after a few hours. They 

 cannot take nourishment nor grow. On the other hand, 

 all the bits which comprise a slice of nucleus commence 

 to contract, and shape themselves like the original 

 Stentor, then form a mouth, and take nourishment, and 

 grow up to be fully-sized, complete Stentors animalcules 

 like that by the cutting-up of which they were formed. 

 This and similar experiments are held to prove that the 

 processes of nutrition, growth, and production of specific 

 form are dependent on the nucleus. In its absence, you 

 may have contractility and active movement for a 

 time, but no repair, no building-up of new material, no 

 directed or seemingly " purposive " movement. Such 

 movements, viz., advance in one direction, arrest, hesitating, 

 or exploring movement to the right and left, followed by 

 rapid retreat or advance in a straight line, are often 

 exhibited by these minute animalcules, and cannot be 

 distinguished in character from those, say, of a fly or even 

 of a mouse. 



These facts throw a great light on the significance 



