DEPARTMENT OE MARIXE BIOLOGY. 155 



Although corals permanently submerged, but above the silty bottom, find 

 favorable conditions for vigorous growth in the moat, there is a constant 

 struggle for life between the corals and organisms that tend to overgrow 

 them. The inimical organisms comprise algse (among which Halimeda is 

 prominent), sponges, tunicates, etc. A collection of these was made for 

 purposes of specific identification. In this struggle the organism that grows 

 the most rapidly is the victor. 



In 1910, 38 colonies in the moat were measured for growth-rate; in 191 1, 

 6 of these ( i Busmilia knorri, i Orhicella annularis, i Maandra clivosa, and 

 3 Siderastrea radians) were dead, i colony was overlooked, and 3 colonies 

 of Oculina diffusa were in bad condition, having been almost smothered by 

 Halimeda and the ascidian done atra. Growth-records on 31 colonies were 

 continued. 



Outer face of the northwest side of Port Jefferson moat-ivall. — Fifteen 

 colonies growing attached to the outer face of the northwest side of the Fort 

 Jefferson moat-wall were measured in 1910. In 191 1, 8 of these were again 

 measured ; 7 colonies were lost in some way. Five of the lost colonies were 

 Favia fragum, living near the base of a colony of Porites furcata. Several 

 or all of these colonies were overgrown and smothered by the Porites, which 

 has a much more rapid growth-rate. 



Reefs off the northzvest face of Loggerhead Key. — A reexamination of the 

 reefs off Loggerhead Key showed that the tops of the heads of Orhicella 

 annularis, exposed during the low-tide period of June 6-8, 1910, had been 

 killed, and that regeneration was taking place along the living edges below 

 the dead areas. 



Nineteen colonies growing on the reefs were measured in 1910; 18 of these 

 were remeasured in 191 1, one of the specimens of the previous year's records 

 having been washed away by a storm. As a new record was added, the num- 

 ber of colonies being measured remain 19, as in 1910. 



PLANUEA CULTURES, I9II. 



As so many young colonies of Favia fragum and Porites astreoides were 

 obtained from the planula cultures of 1910, no attempts were made to obtain 

 additional colonies of these species in 191 1. Fifty cultures containing planu- 

 lae of Agaricia and Porites clavaria were installed, but they were not very 

 successful, probably because of impure sea-water. A total of 28 planulae of 

 Agaricia attached themselves to 5 tiles, which were planted in water 2 or 3 

 feet deep at extreme low tide, off the northwest face of Fort Jefferson moat- 

 wall. As Dr. Mayer has provided apparatus for pumping pure sea-water 

 through a glass circuit, in the future there should be no trouble from con- 

 taminated water. 



TEMPERATURE RECORDS. 



An arrangement was made with Mr. George C. Short, of Fort Jefferson, 

 to take temperature readings, twice daily, in three selected localities, for one 

 year. The readings are to be made at 7 a. m. and 3 p. m., at the Fort Jeffer- 

 son wharf, at the sally-port of the moat, and outside the moat-wall at the 

 flood-gate. These records will furnish accurate information on the tempera- 

 ture condition in three localities being especially studied. 



