314 



MARKETABLE BRITISH MARINE FISHES 



14 to 50 or more miles from the coast. Ripe males are taken on 

 hooks, but not the ripe females, which are caught in nets. The 

 stripping and fertilisation of the eggs are extremely eas\'. The 

 temperature at the surface of the sea at the spawning period was 

 about 54°, and its density i'026g. The mackerel ova although 

 buoyant in the open sea water where they are naturally shed, 



are heavier than those of the lemon 

 dab and other fishes, and sink in water 

 in which the latter float. 



The egg (Fig. 141), is globular and 

 transparent, the yolk is simple but 

 has a single large oil-globule. The 

 breadth of the egg is r22 mm. (not 

 quite o-V inch, more exactly t^-§-jj 

 inch). The eggs hatched on the 6th 

 day at the temperature of 68°. 



The newly hatched larva (Fig. 

 142) is 4'23 mm. long (or not quite 

 4- inch). The mouth is not open ; 

 the oil-globule is at the hinder end of the yolk-sac, and the 

 end of the intestine is just behind the latter. The pigment 

 consists of black and greenish-yellow specks, present on the 

 body and yolk-sac but absent from the fin-membrane. The 

 larvae were not reared in confinement to a greater age than four 

 days (Fig. 143), when the yolk was very nearly absorbed, and 



Fig. 141. — The egg of the Mac- 

 kerel, alive and magnified. 



Fig. 142.— Larva of the INIackerel, newly hatched, alive and magnified. 



the mouth and jaws were developed, but the formation of the 

 fin-rays had not commenced. Pigment was still absent from the 

 fin-membrane. The later stages and transformation of the 

 mackerel do not appear to have been studied. 



Growth and History of the Young.— \ did not procure any of 

 the young of the year while at Plymouth. The smallest mackerel 



