vi PREFACE. 
emy of Science, Salem, Mass.; by the publishers of the 
American Naturalist, 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 Yunicata 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 appendagesare 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. plectos, a fine net, in allusion to the finely 
net- veined wings), and for the Panorpidw, 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. 
