PREFACE. 



The researches of the late Prof. H. de Lacaze-Duthiers (1873, 1897), 

 Prof. G. von Koch (1882, 1897), and Prof. H. V. Wilson (1888) have made 

 us acquainted with many of the early stages in the development of corals. 

 They have served to establish such fundamental facts as the ectodermal 

 origin of the madreporarian skeleton and the sequence of the primary mesen- 

 teries and septa, results which must ever possess an importance to the student 

 of the Anthozoa. But for an understanding of many of the problems of adult 

 coral morpholog}', especially those associated with the relationships of the 

 mesenteries and septa, it has long been desirable that developmental stages 

 later than those studied by the authors mentioned should be investigated. 

 While resident in the West Indies I have followed day by day the postlarval 

 growth of the coral Siderastrea radians (Pallas) for a third of a year, and 

 secured the development of the tentacles and septa as far as the third cycle, 

 and that of the mesenteries to the completion of the second cycle. The 

 results are herein set forth. 



In mau}^ respects the mature polyps of S. radians are of peculiar mor- 

 phological interest, but have never been fully described. An account is 

 therefore first given of the external characters and internal anatomy of the 

 adult colon}', and afterwards of the development of the young polyp from 

 the free-swimming larva. The manner of appearance and the relationships 

 of the tentacles, mesenteries, and septa are considered at some length, their 

 establishment being the principal object of the investigation. 



The work was commenced while Curator of the Museum of the Institute 

 of Jamaica, continued as Bruce Fellow at the Johns Hopkins University, 

 Baltimore, and concluded at the American Museum of Natural History, New 

 York. For facilities afforded in carrying out the investigations I am under 

 obligations to the Board of Governors of the Institute of Jamaica, Prof. W. K. 

 Brooks, of the Johns Hopkins University, and Prof. H. C. Bumpus, of the 

 American Museum of Natural History. The research has been assisted by 

 an appropriation from the Carnegie Institution. 



J. E. D. 



University of Michigan, Ann Arbor, Mich.. U. S. A., 



IITH NOVKMBKR, 1904. 



