sure inside the gill chamber is maintained solely 

 l)y tliese lateral cilia, which form a pumping 

 nieclianism with their synchronized beating over 

 the entire gill surface. 



Local disturbance in the coordination of ciliary 

 motion caused by the change in the ratio between 

 the effective and recovery strokes or by the clianges 

 in the phase of beat results in a drop of pres- 

 sure and decrease in the current velocity. In the 

 absence of valves or any other regulatory devices, 

 the synchronous beat of the lateral cilia over the 

 entire surface of the gills is an essential condition 

 for the effective functioning of tlie gill. 



One can see under the microscope tliat slight 

 mechanical disturbances, such as tapping of the 

 dish in whicli the gill fragments are kept, dis- 

 organize the metachronal wave of the lateral cilia 

 and affect the frequency of their beat. The gill 

 may be compared to a folded tubular sieve, witii 

 the meshes of the sieve corresponding to the ostia 

 surrounded by the lateral cilia. The contraction 

 of the gill muscles brings tlie filaments together, 

 constricts the ostia, and reduces the spaces be- 

 tween the filaments. In this way the passage of 

 water through the gill may be restricted. 



CARMINE CONE METHOD 



The efficiency of tlie lateral cilia can be measured 

 with a simple device kno\\ii as the carmine cone 

 method (Galtsoff, 1926). The method is based 

 on measurements of the velocity of the gill's 

 current in a liorizontal glass tubing introduced into 

 the cloaca. Tlie valves of tlie oyster are gently 

 forced apart until tliey are wide enough to allow 

 the insertion of soft rubber tubing into the cloaca. 

 A wooden wedge is placed between the valves to 

 keep them from closing. The insertion of rubber 

 tubing of a suitable diameter is made by gently 

 rotating it counterclockwise until tlie rubber is 

 slightly pressed against the outside wall of the 

 cloaca. The tubing is then secured in its position 

 by packing the space around it with cotton. A 

 cotton plug is inserted into the opening of the 

 proniyal chamber and is covered with plastic clay. 

 The entire operation can be performed within 2 

 or 3 minutes and is greatly facilitated by narcotiz- 

 ing the oyster in an S to 10 percent solution of 

 magnesium sulfate in sea water. 



The oyster with rubber tubing in the cloaca is 

 tlien placed in a shallow wliite enamel tray filled 

 with sea water and gently tilted back and tnrtli 

 to remove anv air bubbles that may have remained 



under the valves. A small balloon pipette is intro- 

 duced into the rubber tubing to suck out the air 

 bubbles that may be trapped in the epibranchial 

 chamber. The presence of the cloacal current is 

 checked by placing a drop of fine carmine suspen- 

 sion against tlie end of the tubing. The suspension 

 may be added to the gills as well, and in a few 

 seconds a fine carmine cone appears in the cloacal 

 current. 



The end of the rubber tubing is now connected 

 to one arm of an inverted T tube which has a 

 slightly curved glass funnel sealed inside the other 

 arm. This arm is joined to a horizontal glass 

 tubing of known diameter, not less than 15 cm. 

 long and graduated in 0.5 cm. (fig. 139). A 

 thistle funnel filled with fine carmine suspension 

 is attached so the vertical arm of the inverted T 

 tube, and the tube and the funnel are held by two 

 clamps mounted on a heavy stand (not shown in 

 the diagram). The carmine suspension must be 

 released by a pinchcock without disturbing the 

 rubber tubing inserted in the cloaca, and the 

 amount released must be very small in order to 

 avoid back pressure of water in the gills. Because 

 of the frictional resistance of water moving inside a 

 circular tube, the highest current velocity is at 

 the center of the cross sectional area of the hori- 

 zontal tube. A minute quantity of carmine sus- 

 pension or of a solution of nontoxic dye in sea 

 water released from the funnel forms a sharply 

 defined cone inside the tube, the tip of which moves 

 from zero to 10 or 15 cm. mark; the time of its 



Centimetelefs 



Figure 139. — Diagram of the carmine cone method for 

 the study of the efficiency of the lateral cilia of the 

 oyster gill. In order to indicate the position of rubber 

 tubing inside the cloaca, the right valve is not shown; 

 the tank in which the oyster is kept is omitted from the 

 diagram. The funnel with carmine suspension is 

 perpendicular to the plane of the drawing. 



144 



FISH AND WILDLIFE SERVICE 



