iv CONTENTS 



CHAPTER PAGE 



XI. THE SOLUTIONS EMPLOYED ARE NOT PRONE TO 



BE CONTAMINATED BY AIR-BORNE PARTICLES 108 



XII. DOES SILICON, EITHER WHOLLY OR IN PART, 

 ENTER IN THE PLACE OF CARBON INTO THE 

 COMPOSITION OP THE PROTOPLASM OF THE 

 ORGANISMS FOUND IN THE TUBES? . . Ill 



