i897. ARE THE ARTHROPODA A NATURAL GROUP ? 117 



gnathite known as the mandible, which is assumed to be homologous 

 in those classes. Lastly, Jaworowski declares it to be a self-evident 

 fact that the Arthropoda are descended from worm-like ancestors 

 possessing sac-like pouches for breathing air. The opinion of the 

 majority, however, is decidedly in favour of their descent from aquatic 

 non-tracheate organisms. 



Captain Hutton deserves the thanks of zoologists for having 

 elicited the opinions of so many well qualified to speak on this 

 interesting question. But we should like to be present when he next 

 lectures to his students on this subject, to hear how he has managed 

 to reduce these varied views to dogmatic order. 



