PREFACE. 



PREFACE TO THE SECOND EDITION. 



BESIDES a number of minor corrections, this edition has 

 been, it is hoped, improved by the addition of four brief 

 chapters, with illustrations, relating to the centipedes, etc. 

 (Myriopoda), the spiders (Arachnida), the net-veined in- 

 sects without, and those with, a complete metamorphosis, 

 representing several of the smaller orders of the class Insecta. 

 Additional sections on the ctenophores, and on the horse- 

 shoe crab and its allies the trilobites (Podostomata), have 

 also been inserted. 



PROVIDENCE, July, 1887. 



