PREFACE v 
Professors A. 8. Packard, J. H. Comstock, H. H. Wilder, J. I. 
Hamaker, Frank Smith, H. B. Ward, E. L. Rice, H. L. Osborn, 
H. L. Clark, C. W. Hargitt, and H. S. Jennings. Their criti- 
cisms and suggestions have been most helpful and important, 
and I wish to acknowledge a heavy obligation to each of them. 
H. S. PRATT 
HAVERFORD, Pa. 
October, 1901 
PREFACE TO THE REVISED EDITION 
The principal differences between the first and second editions 
of this work consist in the addition of several dissections in the 
second edition, and the revision of the scheme of classification in 
the Appendix. The additional dissections are those of the house 
fly, a spider, the oyster, a sea cucumber, Gonionemus, and a sea 
anemone. 
HAvERFORD, Pa. 
June, 1915 
