THE BEHAVIOR OF A PARASITIC COPEPOD 



41 



placed within the pond. The water can also be seen entering 

 them. 



Before putting any of the infected fish into the tanks, the 

 water in the feed pipes was thoroughly examined in order to 

 determine whether Lernaeopoda edwardsii existed in it. Fine 

 linen bags were tied over the outflows, thereby catching the 

 organisms brought in by the water. The contents of these 

 bags were looked over under the microscope three times daily. 

 Fifteen examinations of these catches did not reveal a single 



Figure 4. Tanks in position 



parasitic copepod, and this convinced me that the water was 

 free from the infection. One hundred parasitized trout were 

 next introduced into each tank, and the covers placed over 

 them. Two days later, the first batch of free swimming larvae 

 was obtained — about two dozen of them. This was on July 

 17th, and almost every day after that until September 5th, 

 when the investigator left the hatchery, from a dozen to three 

 dozen free swimming parasites were secured. 



The animals were scooped up with an open tow net, which 

 was dragged along the surface of the water. The net had an 

 aluminium cup attached to its tapering end. In the bottom of 



