120 THE ADVANCE OF SCIENCE 



tally different significance. Whether not- 

 living matter may pass, or ever has, un- 

 der any conditions, passed into living 

 matter, without the agency of pre-exist- 

 ing living matter, necessarily remains an 

 open question ; all that can be said is that 

 it does not undergo this metamorphosis 

 under any known conditions. Those who 

 take a monistic view of the physical 

 world may fairly hold abiogenesis as a 

 pious opinion, supported by analogy and 

 defended by our ignorance. But, as mat- 

 ters stand, it is equally justifiable to re- 

 gard the physical world as a sort of dual 

 monarchy. The kingdoms of living mat- 

 ter and of not-living matter are under one 

 system of laws, and there is a perfect 

 freedom of exchange and transit from one 

 to the other. But no claim to biological 

 nationality is valid except birth. 

 Mor- In the department of anatomy and de- 



velopment, a host of accurate and patient 

 inquirers, aided by novel methods of 



phology. 



