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. 

 (lY'om a specimen.) 



Conservation in Evolution. — We wish to expand the 

 idea of the hving past into a general conception of the 

 conservative tendency in evolution. There is, it seems to 

 us, a very Uteral 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 

 te — ^what possibiUty of such a hfe would there be — without 

 a persistence of that most primitive manifestation of hfe 

 which we call amceboid movement — the ebb and flow 

 of a protoplasmic tide — so famihar 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 Amoebse ! 



