ARTHROPODA. 307 



10. Can you find any recorded instances of what may be 

 called symbiosis (see 156) between insects and other organ- 

 isms? 



11. Have you any experimental evidence as to how growth 

 can take place in forms with a firm external skeleton such as 

 that of the cray-fish ? 



12. Do you have any reason for thinking that a metamor- 

 phosis is advantageous to any of the Arthropoda? Is it in any 

 respect disadvantageous ? 



13. How is moulting effected? 



14. Habits of the "hermit crabs." 



15. The lobster and its habits. 



1 6. Silkworm culture, value and methods of. 



17. Insects introduced from foreign countries. 



. 1 8. The history of the efforts to find enemies to some of 

 the more important noxious insects. 



19. Relation of insects to the culture of figs. 



20. The structure and habits of the king crab (Limulus). 

 Why is it not to be classed with the true crabs ? 



