Synopsis The present title is a thoroughly revised, enlarged and comprehensive uptodate textbook. This is an indispensable text meeting complete requirements of undergraduate and postgraduate students of Zoology. It has been designed to approach the morphology, anatomy, physiology and development of selected type in a very simple and lucid style. According to the scheme of treatment the important animal types of each phylum have been dealt with first, and efforts have been made to present their elaborate and uptodate account. In the description of animal types special emphasis has been laid on the functioning of organs. General characters and classification and brief description of other important types of the phylum have also been dealt with complete authentic and uptodate account. Separate chapters on topics of significance and general interest pertaining to the phylum have been also added to make the treatment more elaborate. Adaptations of animal type have been discussed in detail to reveal their relation with the environment. It has been the constant endeavour of the authors to furnish maximum substance, keeping in view the limitations of size of the volume. Effort have been made to condense, the matter as far as practicable. The book features both a Text Book and a laboratory guide. It is hoped that this book will not only meet the requirements of Indian students but will also be useful as a guideline to the teachers in their teaching.