THE CARPS 101 



cages, I sunk a large box in the earth and supplied it 

 with a constant stream of water from a natural source. 

 As there are several life histories still to be worked 

 out, I will describe this sunk box method in some detail 

 in the hope that it may be useful to others who feel 

 inclined to investigate for themselves. Selecting a ditch 

 which remained at a fairly constant level all the year 

 round, I led the water from it in a 2-inch pipe to a 

 box sunk in the ground. At the head of the box by 

 means of a board and clay puddle, I held up the water 

 a few inches. The board was pierced by two lead pipes, 

 one a half -inch in diameter, which allowed the water to 

 go into the box ; the other, a two-inch pipe, pierced the 

 board at a higher level, and to one side, and carried off 

 the excess. By this means the water always ran at full 

 bore through the half -inch pipe. The overflow from the 

 box had to be guarded by very fine gauze, twenty 

 strands to the inch, in order to prevent the roach larvae 

 escaping. At first I found the scum on the surface of 

 the water blocked up this fine gauze, and the water 

 flooded over the side of the box. To overcome this I 

 nailed a square tin sieve on to the end of the tank, so 

 that two inches of the sides of the sieve were above, 

 and two inches were below the surface of the water. An 

 overflow hole was cut through the end of the tank and 

 through the side of the sieve in contact with it. The 

 scum now gathered on the solid sides of the sieve and 

 on the end of the tank, and the water welling up through 

 the gauze which formed the bottom of the sieve escaped 



