THE HERRING FAMILY 



173 



is worked even a short distance from land in summer, but be- 

 come more numerous farther out to sea. If the eggs are kept a 

 few days in clean sea-water they hatch, and the larval fish that 

 issues from them has the structure shown in Fig. 89. The artifi- 

 cially fertilised eggs mentioned above hatched in three days at a 



FIG. 89. Xewly-hatched larva of the Pilchard, alive, and magnified. 



temperature of 62. The larva is 3'8 mm. long (slightly over 

 ^j- inch). The yolk is still large, the oil-globule at the hinder 

 end of it, the mouth is not open, and there is no pigment except 

 a few black specks along the back of the slender body. The 

 mouth appeared on the third day after hatching, and on the 

 fourth day the jaws were developed, the eyes were black, and the 

 yolk almost all gone. On the fifth day I put some of the minute 

 creatures gathered from the sea by the tow-net into the tank 

 containing the larvae, and also some minute particles of minced 

 sea worms, and they began to feed. When five days old the 

 larvae were over i inch long, and the yolk was all gone. 

 When feeding the larvae were seen to peck or strike at the par- 

 ticles which they swallowed, so that feeding is a deliberate and 



FIG. 90. Larva of the Pilchard, nine days old, alive, magnified. 



active, not a passive, involuntary process. Fig. 90 shows the 

 appearance of one of the larvae when nine days old. 



The transformation stages of the pilchard have been traced 

 by me in specimens captured at sea near Plymouth. The speci- 

 mens were taken at the surface at night, in a large tow-net made 



