INTRODUCTORY NOTE TO THE ZOOPHYTA. 



Within the past six or seven years the Zoophytes have received more 

 attention from naturalists than any other division of the animal kingdom. 

 The labors of many, if not most of our ablest naturalists, have been 

 directed towards an investigation of the humblest forms of animal life. 

 This fact, combined •with the recent improved methods and means for 

 research, would alone be prophetic of the most signal advances in this 

 group ; indeed, our knowledge of all these forms has been so modified, as 

 well as increased, that previous writings need rather to be re-written than 

 revised. Dana, Agassiz, Milne Edwards, Forbes, Dalyell, Midler, Bztsch, 

 and others, not to mention the continued labors of older observers, have 

 effected these changes in this group. 



The work ()f Daiia is most excellent, and will remain a standard of au- 

 thority in this department for a long time to come. Aside from the many 

 details of structure, in it may be found the first and best j^hilosophical 

 exposition of the relations of organic development with these lower plant- 

 like forms. Had this work been better known in Europe, there would have 

 been saved the constant repetition of the most grave errors. On the labors 

 of Agassiz no comment need be made ; those who are in this department, 

 whether as minute Anatomists or philosophical Zoologists, will not fail to 

 understand and appreciate him. In the same field is Busch, who was 

 extended his brief though excellent labors over the three classes of this 

 whole group ; as for the remaining authors mentioned, excepting Midler, 

 their position in this department has long been established. Midler's 

 researches have been mostly on the Echinoderms, and the careful tracing 

 of the phases of their development and metamorphoses ; but where so much 

 has been done, I fear the limits of this book will preclude full details with 

 this class. 



This note would be unnecessary, were it not to show that I do not ignore 

 the changes and advance which have been made in this group within the 

 past few years ; and more especially so, as I have allowed, in this edition, 

 the classification to stand as in the original. Any great changes of this 



