1 84 THE TROUT 



out, and that there is a grand litter of empty shells. 

 These you will proceed to remove with the egg 

 extricator (fig. 10). 



Soon the alevins will be seen to crowd together 

 in dense throngs about the sides and corners of the 

 trays where there is most shade to be had. This 

 ' packing ' of the alevins is a healthy sign. Closely 

 observed, their pectoral fins will be seen to be all 

 working at a tremendous pace ; and it is in this way 

 that each individual alevin assists in the work of 

 respiration not only for itself but also for the rest of 

 the shoal. In fact, as Sir James Maitland put it, 

 ' the mass is a gigantic co-operative breathing asso- 

 ciation.' 



Gradually the yolk sac will grow smaller, becoming 

 incorporated in the body of the fish. The length of 

 time occupied by this process is regulated chiefly 

 by the temperature of the water. From four to six 

 weeks is a common time to elapse before the little 

 fellows begin to feed, which, if they are strong, 

 should be shortly before the final disappearance of 

 the sac. 



During the period of alevinage your labours will 

 again be light. Snugly secure the alevins remain 

 cribbed in the hatching-tray, the sides of which are 

 high enough to prevent them from jumping out. 



