12 



Marine Invertebrates 



should be used. It is advisable to have the silk part of the net sewn on a 

 canvas collar folded over the metal ring and fastened to it by means 

 of buttons. The lower end of the net is also made of 

 a canvas collar which is slipped over the metal bucket 

 and fastened to it by a clamp ring. The bucket has 

 windows covered with bolting silk and is provided with 

 a stop cock for draining. A small glass bottle or jar 

 may be used instead of a bucket. Nets one foot in 

 diameter are the most convenient ones to handle from 

 a small boat. 



The plankton trawl. Planktonic forms living just 

 above the bottom may be collected by means of a 

 plankton net mounted in a horizontal position on a 

 frame attached at right angles to a sheet of galvanized 

 iron. When the plankton trawl (Fig. 16) is dragged it 

 slides over the bottom and catches the organisms which 

 otherwise escape capture. The metal sheet protects 

 the net which does not come in contact with the bot- 

 tom and therefore may be made of fine bolting silk. 

 The glass bottomed box. In shallow waters the ob- 

 servation and collection of bottom animals are greatly 

 facilitated by using a water tight box with a pane of 

 plate glass fitted in the bottom. The dimensions and 

 shape may vary to suit individual purposes. The box 

 used by the author is 1 1 inches high with square bottom and top, 9x9 

 and n x 11 inches respectively (Fig. 17). It is fastened to a boat by 

 a short line and is placed in the water with the glass side down. It 

 smooths the ruffled surface of the water. 



Goggles. Goggles (Fig. 18) are widely used in the Orient by pearl- 



Fig. 15. — The 

 plankton net. 



Fig. 16. — The plankton trawl. 



oyster fishermen and may be used to aid in the collection and observation 

 of shallow water animals inhabiting the ocean floor. Those with wooden 

 frames are the most convenient for they may be carved to fit the eye- 

 sockets. Condensation of vapor on the inside may be avoided by follow- 

 ing the method of the Philippine divers who rub the glass with tobacco 



