LIVING ORGANISMS 25 



existence, the typical form is nearly spherical, 

 as seen in the ovum, and also in many of the 

 minute cells of which the body is composed. 

 Living matter never assumes crystalline forms; 

 it does not grow like a crystal, by the deposition 

 of new matter on its surfaces, but by absorbing 

 matter into its substance and usually trans- 

 forming this into matter like itself. A crystal 

 does not transform, and it grows by the 

 deposition of new layers on its surface ; 

 living matter can transform, or assimilate, 

 and it can grow by the transformed matter 

 becoming part of its substance. It is re- 

 markable, however, that dead matter may 

 assume forms very similar to the forms of 

 living matter. In certain media crystallisable 

 substances may take on organic shapes, and 

 various mixtures of soaps, gums, etc., may 

 form a froth which, under the microscope, may 

 show forms very similar to that seen in living 

 stuff. In some circumstances even the move- 

 ments of living matter may be imitated. 

 Thus, a highly complex substance called 

 protagon can be extracted from yolk of egg 

 by hot alcohol. If a minute portion be 



