CORALS AND CORAL REEFS — VAUGHAN. 209 



culture jar, on the bottom of which was a terra-cotta disk having a 

 central perforation that fitted over the head of an iron stake. 



The disks ^ had a diameter of 8 inches and were placed in jars, the 

 inside diameter of which was about 8^ inches, and the depth about 

 8| inches. After the bottom of a jar had been covered with the 

 cleanest sand obtainable, a disk was placed in the jar, and the central 

 perforation and the space between the periphery of the disk and the 

 sides of the jar were filled with sand to the level of the upper sur- 

 face of the disk. Filling these spaces is necessary, as the planulae 

 tend to settle in depressions. After this preparation, pure sea water 

 was gently pouved in through a funnel until the jar was nearly full. 

 Then the extruded planulae were taken with a pipette from the vessel 

 containing the j)arent colony and placed in the culture jar prepared 

 for their reception. 



To get the best results, the water in the culture jar should be 

 changed at least once a day. This may be done by several devices. 

 In order not to draw off the x^lanulae, which are very small, a bag 

 of fine-mesh bolting cloth must be affixed to any tube used in with- 

 drawing the stale water. ^ One method was to siphon off the stale 

 water with a rubber tube, the end of the tube inserted into the cul- 

 ture jar having been drawn over one end of a glass tube, the other 

 end of wliich was enveloped in a bolting-cloth bag. The table on 

 which the culture jars stood was provided with a gutter into which 

 the water drawn off was discharged and was ultimately carried out- 

 side the building by a pipe through the floor. After a jar had been 

 emptied to within an inch of the disk it was refilled with fresh sea 

 water. This method causes a change in the level of the water, and 

 the pouring stirs up the unattached planulae. A second method was 

 to withdraw the old water by a glass siphon resting on the upper edge 

 of the jar, the siphon having been rendered nonempty ing by having 

 its outer end bent upward. Fresh seawater was added by a siphon 

 extending to the bottom of the culture jar from a supply jar placed 

 at a higher level. By this method a constant level was maintained in 

 the culture jars, the old water was drawn off from the top, while the 

 new water was added at the bottom. This method is illustrated by 

 pi. 19, figure A. 



Two other devices were used for changing the water — one of them 

 replenished it without, the other with change of level, but they will 

 not be described here. All four of the methods tried were successful, 

 and the preference between them was not determined. Pure water is 

 necessary and occasional stirring of unattached planulae may be bene- 

 ficial. It is imperative that the sea water used in these cultures be 



^ Vaughan, Carnegie Institution of Washington Year Book No. 9, 1911, pp. 141, 142. 



