146 Phylum Coelenterata 



changed by one of several devices. In order not to draw off the planulae, 

 which are very small, a bag of fine-mesh bolting cloth must be affixed 

 to any tube used in withdrawing the stale water. One method was to 

 siphon off the stale water with a rubber tube, the end of the tube inserted 

 into the culture jar having been drawn over one end of a glass tube, the 

 other end of which 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, ultimately flowing outside the building 

 through a pipe through the floor. After a jar had been emptied to within 

 an inch of the tile, it was refilled with fresh seawater. This method 

 caused a change in the level of the water, and by the pouring stirred up 

 the unattached planulae. 



A second method, which was the one usually employed, was to with- 

 draw the old water by a glass siphon resting on the upper edge of the jar, 

 the siphon having been rendered non-emptying by having its outer end 

 bent upward. The inner end of the siphon was enclosed by a bolting 

 cloth bag. 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. A third method was to have inside the culture jar a 

 tantalus siphon emptying through the side of the jar near its bottom. 

 Fresh water was siphoned into the culture jar from supply jars placed at 

 a higher level. When the water in a culture jar had reached the level 

 of the upper curvature of the siphon, it began to run out and continued 

 to flow until the level of the open end of the siphon in the jar was 

 reached. The jar was then refilled by the afferent siphon until the level of 

 the upper curvature of the tantalus siphon was again reached, when the 

 water again began to flow out. This method caused a rise and fall 

 in the level of the water. A fourth method was to cut the bottom out 

 of a culture jar and to place the glass collar thus produced over a tile 

 in a jar of larger diameter, the bottom of which had previously been 

 covered with sand to a depth of an inch or slightly more. The tile 

 and its surrounding collar were sunk into the sand until the upper sur- 

 face of the tile and the upper surface of the sand were level with each 

 other, while the level of the upper edge of the collar remained slightly 

 higher than that of the enclosing jar. Water was siphoned into the 

 collar from supply jars, and filtered through the sand filling the space 

 between the collar and the side of the inclosing jar. When the level 

 of the upper edge of the jar was reached, the water overflowed. This 

 method maintained a constant level of water, drew off old water at the 

 bottom, and added new water at the top. 



All four methods were successful, but as the second was somewhat 



