.MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 405 



for weeks or months at a time, by simply renewing the fresh-water lost by evaporation. The 

 functional activity of numerous symbiotic unicellular algae (Zooxanthdla), presenl in the endo- 

 dermal tissues of each species, is sufficient to maintain the water in a tit state of aeration and puiity. 



For typical reef -building corals, such as species of Madrepora, Poritt s, .'/•< andrina, and Orbi- 

 ceila, tin- most convenient collecting spots are among the small group of coral islands, termed 

 ■■( ays." beyond Kingston I [arborand Port Royal. From the reefs surrounding these over twenty 

 further species are to be obtained, and other localities around the island yield practically the same 

 forms; also at certain places in Kingston Harbor reef-building corals occur at accessible depths. 

 A-> would be expected from the uniformity of climatic conditions, the Jamaican corals are such as 

 are generally distributed throughout the entire West Indian region. 



All the species here studied have been examined in their living condition, and usually from an 

 abundance of material. In most cases the colonies were kept alive for some time within the labora- 

 tory, so that the varying aspects of the polyps during expansion and retraction could he observed. 

 Much indeed of the character of the polyps is to be obtained in this way, which is impossible from 

 retracted preserved polyps. 



Most of tin 1 material for anatomical study was preserved with the polyps narcotized in a 

 partly expanded condition, in order to render possible a better study of the relationships of the 

 various organs and of the skeleton. When killed otherwise the polyps shrink deeply within tin 1 

 calice. the stomodamm becomes flattened by resting upon the central portions of the skeleton, and 

 the arrangement of the mesenteries, etc., can be ascertained only with difficulty. For narcotiza- 

 tion I have employed either magnesium sulphate or menthol, and both methods give satisfactory 

 results. The use of menthol as a narcotic is very simple. It is merely necessary to sprinkle a 

 few crystals on the surface of the water, when the reagent becomes slowlv absorbed and jjradu- 

 ally anaesthetizes the polyps; pure formed is then added to the water in sufficient proportions to 

 make a 5 per cent, solution, and the polyps usually undergo no further change. The polyps may 

 retract and shrink slightly if the process of narcotization is incomplete, but never to the same 

 extent as if preserved directly. Though very desirable for museum purposes, a polyp expanded 

 to its utmost offers no advantages for anatomical and histological study. The tissues in this con- 

 dition are so attenuated as not to permit of the characteristics, especially those of the musculature, 

 being determined with the same facility as in only moderately expanded examples. Usually the 

 polyps expand fully only at night, or when placed in the shade, and the process of narcoti- 

 zation requires several hours. At night it was generally found convenient to add slowly the 

 crystals of magnesium sulphate or menthol and allow them to act upon the polyps until morning, 

 when the addition of formo] brought about no retraction. 



The proper preservation of the soft tissues of the Madreporaria has always been a matter of 

 some difficulty, but the employment of formol is found to be fairly satisfactory. I have adopted 

 it as a 5 per cent, solution in either fresh or sea water. Especially is the reagent serviceable on 

 account of its penetrative powers; in all cases the preservation of the internal tissues was equal 

 to that of the external, the ciliation being recognizable in most instances. There is an element of 

 uncertainty, however, as to how long the histology will remain perfect in the formol solution 

 alone. In some instances material which had remained in the original preservative fluid for 

 five or six months lias been found satisfactory for microscopic study, but in others a slight 

 maceration has taken place. In this latter case the details of the anatomy and coarser histology 

 can be still made out, but the more minute histology is imperfect. The possibility of maceration 

 holds especially for forms like Porites, which exude a large amount of mucus on preservation. 

 To guard against such risks, I have found it necessary to transfer the specimens, shortly after 

 preservation in formol. through the different grades of alcohol up to 90 per cent. Where material 

 intended for histological research has to be kept for some time this is undoubtedly desirable. On 

 the other hand, for museum purposes expanded coral polyps, anemones, and medusae have been 

 kept in a solution of formol for several years without any obvious deterioration. 



i lists of these see the papers by PourtaK-s, Agassiz, Quelch, Duchassaing and Michelotti, Yen-ill. ( rregory, ami 

 Vaughan, referred to in the Bibliography. Tin- figures and references to corals in the old natural hist erics of Jamaica 

 by Sir Hans Sloane ' 1 7i >7 ami Dr. Patrick Browne ' 1756) are well worthy of notice, as also those of Lesueur (1820). 



