406 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



An aqueous solution of corrosive sublimate or corrosive acetic has also been employed with 

 great advantage, in that it fixes the tissues so completely that on decalcification there is little or 

 no alteration in the relationships of the different organs. It is much superior to t'ormol or alco- 

 hol in this respect. Before commencing the decalcification of material which has been in alcohol 

 or forniol for some time, I have often found it advantageous to pass it through a solution of cor- 

 rosive sublimate. 



Decalcification has generally been performed in a weak solution of hydrochloric or nitric acid, 

 after the material has been thoroughly hardened. The acid is added drop by drop to a fragment 

 of the coral still in the preservative fluid in sufficient quantities to maintaina slight effervescence. 

 From one to two days are required for the decalcification of small pieces of porous corals, such 

 as Madrepora and Porites, whereas the decalcification of dense coralla, like those of Siderastrasa 

 and Ociilina, occupies three or four days. Where it has been desirable to carry out the decalci- 

 fication with special care, as in investigations of the calicoblast layer and skeletal matrix, very 

 weak solutions of acetic and chromic acids have been employed, and then the process requires a 

 much longer period. When, as is usually the case, perforating algal matter occurs within the 

 skeleton, it is advisable to remove this from time to time, so as to keep a fresh calcareous surface 

 exposed. 



If decalcification of properly fixed material be slowly carried out, there is little or no dis- 

 turbance of the primary relationships of the. soft parts. After a few attempts. I concluded that 

 nothing was to be gained by making preparations of the hard and soft parts in situ, such as are 

 obtained by embedding fragments of a colony in Canada balsam and then grinding down to micro- 

 scopic thinness. All the figures of the sections are, so far as concerns the relationships of the 

 soft and hard parts, actual reproductions of camera lucida drawings. The irregularity in outline 

 of many of the septal invaginations can be understood when one considers how generally the 

 septa are provided with spines or granules. 



Much of the work has been carried out while in Jamaica, and the remainder during the 

 academical year 18'.»U— l'.tOO. in Professor Brooks's biological laboratory at the Johns Hopkins Uni- 

 versity." My thanks are due to Prof. W. K. Brooks for many valuable suggestions and much 

 kindly interest during my stay in Baltimore; also to Prof. A. C. Haddon, of the Royal College 

 of Science, Ireland, and Prof. (i. B. Howes, of the Royal College of Science, London, for much 

 assistance and encouragement from time to time during the progress of the work. I am indebted 

 to Rear Admiral (then Commodore) H. N. Henderson for generously affording me facilities for 

 collecting in the waters around Port Royal and the Cays beyond. Mr. T. Wayland Vaughan, of 

 the United States Geological Survey, has assisted me in the specific determinations. In his recent 

 account of the fossil corals from Curacao (1901), and also of the stony corals of (he l'orto Rican 

 waters, Mr. Vaughan (1901<z) has dealt with the difficult subject of the synonymy of West Indian 

 corals. 



The paper is divided into two parts. The first is devoted to a more general description of 

 the external characters and morphology of coral polyps, so far as the material available will 

 permit, and the second to a description of the external characters and internal anatomy of certain 

 representative species. To the former a few notes on larva' and postlarval development are 

 added, which, although incomplete, assist in an understanding of the significance of many of the 

 adult features. In a large measure, also, I have carried out comparisons with the better-known 

 Actiniaria. The polyps of the two groups an 1 so closely alike that a knowledge of the characters 

 in the one often assists in throwing light upon conditions in the other. In the second or system- 

 atic part, I have ventured to indicate some of the broader lines of relationships among theMadre- 

 poraria, suggested by the new facts obtained, and have attempted for the first time generic 

 diagnoses in terms of the polyp. It will be understood that where generic characteristics are 

 given they have reference only to the representatives here studied. The isolation under which the 



"Since the presentation of the paper the studies have been continued, and results of some importance obtained, 

 which amplify certain of those here given, particularly those on growth by gemmation and fisMparity. They are 

 referred to in foot-notes on various pages. 



