36 WHAT IS LIFE 



honeycomb, while the solid forming the residuum 

 has a refractive index of a little over 1-6. There- 

 fore, it only regains its full transparency when the 

 water is replaced by a liquid of high refractive 

 index, such as an essential oil or phenol. A simi- 

 lar change may be effected by pouring white of 

 egg into boiling water or absolute alcohol, and is 

 attended with the same optical results." 1 



Such, then, are the chief characteristics revealed 

 by our study of the amoeba. It moves, it responds 

 to stimuli, it breathes and it feeds, it carries on 

 complicated chemical processes in its interior. It 

 increases and multiplies and it may die. 



These observations are not only true of the 

 single-celled organism but of the multicellular and 

 they are equally applicable to the animal and to the 

 plant. 



Perhaps, however, it may be right to call the 

 attention of those unaccustomed to consider bio- 

 logical problems to the difference apart from all 

 question of multitude or number of cells which 

 exists between the unicellular and the multicellular 

 organism. In the former case all the functions 

 which the animal performs are carried out by the 

 single cell. To put matters plainly this one cell 

 is brains, lungs, heart, stomach, intestines and 

 reproductive mechanism. In the multicellular 



1 Hartog. 



