146 FISH CULTUEE 



ing lines represent the contour of the skull. A 

 little later a curving black line is attached to the 

 bottom of the V and a perfect Y is the result. 

 The tail of the Y is the backbone. "With suc- 

 ceeding days the rude outline of the skull and 

 backbone develops, until at length a perfectly 

 formed fish is visible, wrapped almost com- 

 pletely around an oval ball (the yolk-sac). 



Active life is then apparent. At first it is 

 manifested at short irregular intervals by oc- 

 casional tremors through the little fish ; then, in 

 sudden, convulsive, jerky movements which in- 

 crease in frequency until just before it emerges 

 from the shell. As soon as the little fish has 

 acquired sufficient strength it breaks the shell 

 and begins to emerge, tail first. It works vigor- 

 ously for a short time, then rests, then resumes 

 activity and so, alternately struggling and rest- 

 ing, it finally frees itself wholly from the mem- 

 branous envelope in which it began existence. 

 To break through the shell of the egg tail first, 

 is nature's method of bringing a perfectly 

 healthy fish into the world. 



Why does a healthy fish always issue from the egg 

 tail first? A plausible answer is that by so doing 



