Common English terms even if descriptive, when used in their ordinary dictionary sense, have not been included as a rule; but this is subject to many exceptions. Latin terms and derivatives, even if used in their usual sense have been generally included; but compounds made up of adequately defined descriptive terms are generally omitted. Adverbial or adjective forms have been omitted whenever it has been considered safe, and so have terms prefixed by sub-, supra- and the like, indicating degree or position. In doubtful cases the terms have been included and defined. All terms of venation are, so far as possible, reduced to the Comstock system which is the only one that has been satisfactorily worked out for all orders, and a series of figures is added to explain this system so far as seems necessary. It has not been considered feasible to determine the proper use of terms applied differently in different orders or families; that is scarcely within the scope of a work of this kind. Terms used in embryological and histological study have been included only so far as seemed necessary to an understanding of the general works, and no attempt has been made to cover the terms applied to musculature and other details of microscopic structure: this has seemed rather to be outside of the scope of the present essay. All color terms are reduced so far as possible to terms of the Windsor and Newton system of water colors which are standard in the English-speaking world, and the color plate shows solid blocks of those colors that seem necessary to explain all modifications except metallics, blacks and whites. {Scanner's note: color plate may be excluded, partly because it is in poor condition.} The figures illustrating body structures and other details have been drawn under my supervision by Mr. John A. Grossbeck, and are meant to be guides merely - else the glossary would exceed its scope. In the admission that the work is incomplete, no apology is intended for its publication; it is merely a statement of fact to encourage constructive rather than destructive criticism. It is hoped that those who note errors or omissions will communicate them to the writer so that when another edition is needed, as it will be before many years are past, a standard work may be possible. JOHN B. SMITH, Sc.D. New Brunswick, N.J. April 1906 EXPLANATORY. Definitions of general application are as a rule given first, where more than one is necessary; next those of limited use, and finally the specific meaning in each order in which there is any notable difference.