228 CRUSTACEOUS ANIMALS. 



Mocking the eye ? Alas ! before the veil 



Of denser clouds shall hide thee, the pursuit 



Of the keen swift may end thy fairy sail. 



Thus on the golden thread that fancy weaves 

 Buoyant, as Hope's illusive dattery breathes, 



The young and visionary poet leaves 



Life's dull realities, while seven-fold wreathes 



Of rainbow light around his head revolve. 



Ah ! soon at Sorrow's touch the radiant dreams dissolve. 



Questions. — 1. Upon what is the division of insects into orders 

 ounded ? 2. What are the characteristics of the first order ? .3. Se- 

 cond ? 4. Third ? 5. Fourth ? C. Fifth ? 7. Sixtli ? 8. Seventh •" 

 9. Describe the wings of butterflies. 10. Describe ephemeral flies.-* 

 IL What is worthy of notice in ants, wasps, and bees ? 12. How is 

 the buzzing of flies produced i 13. How do aptera insects often ap- 

 pear on plants .'' 14. How are spiders distinguislied from all other 

 insects 'i 15. How is the web of the spider produced .'' 16. Describe 

 the aerial excursions of spiders. 17. What is the gossamer, and where 

 seen .' 



LESSON lOL 



Crustaceous and 3IoUuscous Animals. 



Mu'cous, slimy, viscous or glutinous. 



The Crustaceous animals have been sometimes included 

 in the class of insects, to which they have indeed many 

 strong points of resemblance. They deserve, however, a 

 separate consideration, both on account of their size and im- 

 portance, and of some anatomical differences of structure. 

 They have articulated limbs, antennas, and jaws, similarly 

 formed to those of insects. But they breathe by means of 

 gills, and have a regular, double circulation ; in which par- 

 ticulars they difer from insects. Among the most familiar 

 examples of this classL are the lobster, craw-lish, and what 

 is usually called the horse-shoe. They are covered by a 

 pretty thick, firm shell, which envelopes them completely. 

 As this shell is incapable of growth, it is occasionally chang- 

 ed, to make room for the constant increase in size of the 

 aniiflal. It is thrown off, and their bodies remain for a time 

 entirely naked, and exposed in a soft and defenceless state. 



