Excerpt from A Manual of Zoology The favor with which the first and second American editions of Hertwig's Zoology have been received has led to a thorough revision of the whole with a close comparison with the latest German edition. In this there have been introduced many new features bringing the work up to date. These include a discussion of Mendelian inheritance, many modifications in the account of the theory of evolution, and a considerable enlargement of the Protozoa and especially of the pathogenic forms, making the volume of more value to the student of medicine. To have included these without changes elsewhere would have resulted in a much larger volume. But the demand in American colleges has been for a smaller work and so a reduction has been made in two ways. There has been a condensation by the elimination of unnecessary words and phrases and by the omission of considerable matter of minor importance. Then there has been the recognition of the fact that the book has two uses, one in the class room the other as a reference work. The two classes of matter have been distinguished by difference of type. No attempt has been made to bring the systematic names into accord with the latest vagaries of the systematists. No useful and could be served by changing or transferring the well-known names of Echidna, Coluber, Amia, Homarus, Unio, Holothuria, Am ba, etc., while the confusion this would introduce would be enormous. It should be understood that while the revision is based upon the German edition of Professor Hertwig, he should not be held responsible for any changes introduced. The whole responsibility for these rests upon the American reviser.