Vlll. PREFACE. 



the alternation of generations, the embryology and develop- 

 ment of the Zoophytes, and the nature and functions of 

 their special organs. The varied forms and singular 

 properties of the Thread-Capsules in the Polypes and the 

 Medusae, in particular, have excited my own admiration. 



The curious observations of Sir J. G. Dalyell and other 

 zoologists on the propagation of the Hydroid Zoophytes, 

 might seem to render those recorded in this volume need- 

 less ; but the words of the indefatigable naturalist just 

 named warrant the multiplication of observed facts. 

 Speaking of the mysterious appearance of certain Medusce 

 in connexion with Tubulariee, he says, " Were similar 

 instances recorded, our embarassments might be relieved ; 

 for more frequent, easier, and stricter investigation being 

 admitted, doubtless such a train of discovery, and thence 

 the solution of what are to us the most abstruse problems, 

 would follow." 



The plates have been all drawn from living nature, with 

 the greatest attention to accuracy. They are twenty 

 eight in number, of which twelve are printed in colours : 

 they comprise about two hundred and forty figures of 

 animals and their component parts, in many instances 

 drawn with the aid of the microscope. 



London: March 30ih, 1853. 



