The Era of Invertebrate'^ 



may be only apparent, not real, due to the diffi- 

 culty of their preservation. For there is much 

 reason to suppose that insects had their origin 

 in the water ; many of the more generalized 

 forms among living species deposit their eggs 

 in the water, and there pass the early part 

 of their lives, preparatory to the final trans- 

 formation, while the wings are believed to 

 have been developed from breathing and 

 swimming organs. 



We know even that there were such soft 

 and perishable creatures as jellyfishes floating 

 in the waters that then covered the face of the 

 earth, for indications of their presence have 

 been preserved in the shape of certain star-like 

 markings in the rocks, which represent casts of 

 the interior of the bodies of these animals 

 formed by the fine in filtering mud. The highest 

 forms of life of this period were trilobites, a 

 group of animals belonging with the crabs, 

 whose nearest living relative is the king crab, 

 Limiiliis pohjiyliemiis, so common at some places 

 on our Eastern coast. The resemblance be- 

 tween the two is best seen by comparing very 



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