VI PREFACE. 



emy of Science, Salem, Mass.; by the publishers of the 

 American Xuturalist, and by the Boston Society of Natural 

 History, while forty of the cuts of birds have been electro- 

 typed from the originals of Coues' Key, and Tenney's Zoology. 



Measurements are usually given in the metric system ; in 

 such cases the approximate equivalent in inches and fractions 

 of an inch are added in parentheses. 



Should this manual aid in the work of education, stimu- 

 late students to test the statements presented in it by person- 

 al observations, and thus elicit some degree of the inde- 

 pendence and self-reliance characteristic of the original in- 

 vestigator, and also lead them to entertain broad views in 

 biology, and to sympathize with the more advanced and 

 more natural ideas now taught by the leading biologists 

 of our time, the author will feel more than repaid. 



BROWN UNIVERSITY, 



Providence, R, I., October 25, 1879. 



PREFACE TO THE FIFTH EDITION. 



MORE radical changes have been made in this than any 

 former edition. The Tunicata have been transferred to a 

 position next below the Vertebrates in the group Chordata. 



The Merostomata, together with the Trilobites, have been 

 placed in a class called Podostomata (in allusion to the fact 

 that the head and mouth appendages are foot-like). Their po- 

 sition is between the Crustacea and Arachnida. The branch 

 Arthropoda is divided into six classes, viz.: 1, Crustacea; 

 2, Podostomata; 3, Malacopoda ; 4, Myriopoda; 5, Arach- 

 nida; 6, Insecta. The orders of insects have been increased 

 from eight to sixteen, according to the arrangement on pp. 

 365, 366. For the order of Mayflies we propose the name 

 Plectoptera (Gr. plecfos, a fine net, in allusion to the finely 

 net -veined wings), and for the PanorpidcB, the ordinal 

 name Mecoptera (Gr. mecos, length, in allusion to the long, 

 narrow wings). Numerous minor changes and corrections 

 have also been made. 



PROVIDENCE, June, 1886. 



