THE WONDER OF LIFE 621 



become like a gizzard, with thick and muscular walls. 

 This is associated with a unique reduction of the front 

 of the breast-bone, and a consequent lessening of the 

 area for the attachment of the muscles of flight. 



FIG. 98. New Zealand Lizard, Sphenodon or Hatteria, an archaic 

 reptilian type, sole survivor of the ancient race of Rhynchocephalia. 

 (From a specimen.) 



Conservation in Evolution. We wish to expand the 

 idea of the living past into a general conception of the 

 conservative tendency in evolution. There is, it seems to 

 us, a very literal sense in which we may think of the higher 

 animals as heirs of all the ages. Particularly effective 

 modes of vital behaviour, some of which made a fortune 

 in their day, yet did not save their possessors from utter 

 ruin, have been caught up by collateral relatives and 

 handed on as a legacy from by-gone ages to the higher 

 animals. Where, for instance, would a higher animal 

 be what possibility of such a life would there be without 

 a persistence of that most primitive manifestation of life 

 which we call amoeboid movement the ebb and flow 

 of a protoplasmic tide so familiar to students of biology 

 in amoebae and white blood corpuscles ? How long would 

 a higher animal survive without its body-guard of phago- 

 cytes ? Nor could it have become what it is, had not its 

 embryonic nerve-cells flowed out into nerve-fibres ; just like 

 exploring Amoebae ! 



