32 Instinct and Intelligence 



It is well in passing from the consideration 

 of unicellular to multicellular beings to bear 

 the above principles in mind, for they apply to 

 the reproduction of all multicellular animals. 

 Germinal cells alone possess the power of 

 giving rise to a being resembling more or less 

 closely in the structural, and potential powers 

 of the stock from which these cells have been 

 derived, powers which they pass on to succeed- 

 ing generations. The mass of cells which 

 form the various tissues and organs of an 

 animal's body, including the nervous system, 

 are known as somatic cells; worn-out or injured 

 somatic cells are replaced by fresh cells pro- 

 duced by asexual division of neighbouring like 

 cells, but are incapable of giving rise to new 

 beings. At the same time, we must never forget 

 that the living protoplasm of every form of 

 animal cell possesses a certain proportion of 

 elements having mnemic and instinctive 

 functions. 1 



1 It has been assumed that a fertilised cell, such, for instance, 

 as that of a human being, which has a diameter of about 

 ^V mm., is too minute in size to contaii a sufficient amount of 

 matter to produce a man with all his structural and mental 

 qualities. This idea, however, is not entertained by those best 

 qualified to form an opinion on the subject. Prof. J. G. 

 M'Kendrick states that taking the average cubical diameter of a 



