FISH HATCHING ON A MODEST SCALE 431 



When the eggs have all hatched into alevins, some 

 little rearrangement of the hatching boxes falls to be 

 made. A few points of management appropriate to the 

 period before the fish becomes a " fry " may also be re- 

 ferred to. When the embryo fish bursts its shell it is 

 not in the least like a fish. To the blunt head, with its 

 staring black eyes, and the thin transparent body, is 

 added an elongated bag larger than the fish, containing 

 sufficient nourishment to last it for a further space of 

 fifty days. The fish is not perfect until this bag, or 

 umbilical sac, is wholly absorbed. During the period 

 of absorption the instinct of the little creature, which 

 can only wriggle spasmodically on its side, drives it to 

 hide in any minute crevice that it can find. Now it is 

 that previous careful smoothing of all angles and exact 

 fitting of all fixed and movable parts of the box will 

 be seen to be of the utmost importance. For into every 

 corner and crevice the alevin will attempt to wriggle, 

 and success, or partial success, will almost certainly 

 have fatal results. The best protection for them at this 

 time, beyond careful construction of the boxes, will be 

 absolute darkness in the hatchery. 



In those boxes containing grilles it will be observed 

 that, as the eggs hatch out, the alevins drop through 

 between the glass tubes to the bottom of the box, and 

 the syphon tube will now be in constant use removing 

 the empty egg shells. When the eggs are all hatched, 

 the glass grilles and the frames which carry them are 

 removed, thoroughly cleaned, and carefully put away. 



