40 



NATHAN FASTEN 



III. HATCHING THE ORGANISM 



In order to obtain enough material for experimentation, it 

 became necessary to hatch the copepods artificially. The first 

 efforts were confined to attempts to hatch the parasites in 

 aquaria within the hatchery, but this proved a failure. Con- 

 ditions here were far from normal, and the attempt was soon 

 abandoned. 



Outdoor experiments were next tried. Two large tanks were 

 constructed, which were eight feet long by. three and one-half 

 feet wide and two and one-fourth feet high. The frame of 



Figure 3. 



Hatching tank 



these tanks was made of wood, while the sides consisted of 

 coarse wire netting. The interior faces were lined with fine 

 linen gauze so as to prevent the escape of any copepods. Figure 

 3 is a photograph of one of the tanks. 



Simply stationing these tanks in one of the open hatchery 

 ponds proved insufficient, for, through lack of circulation, trout 

 placed into them very quickly succumbed. So the tanks were 

 placed in such a way that the water from some feed pipes ran 

 directly into them.. This arrangement proved entirely satis- 

 factory. Figure 4 shows the manner in which the tanks were 



