130 POPULAR ILLUSTRATIONS OF THE LOWER FORMS OF LIFE. 



The reader who wishes to know more about the sub-kingdoms 

 treated of in this volume will do well to consult the " Icones His- 

 tiologicse " of Kolliker ; Professor Greene's work on the Protozoa 

 and Coelenterata ; Professor Huxley's " Elements of Comparative 

 Anatomy ;" and Professor Owen's Lectures on the Invertebrata. 



