126 



BULLETIN OF THE BUREAU OF FISHERIES. 



fully differentiated, extends more than halfway around the circumference of the yolk 

 sphere. Although the blastoderm early covers a large portion of the surface of the yolk, 

 the blastopore does not close until the embryo is well formed and segmentation of the 

 body has begun (fig. 94). The closure of the blastopore occurs within 16 hours after 

 fertilization. At this time the embryo extends fully two-thirds around the circumference 

 of Cue yolk sphere. Figure 95 illustrates an egg shortly after the blastopore is closed. 



As the time of hatching approaches the embryo increases in length until it makes 

 more than a complete turn within the egg membrane. It becomes relatively opaque but 

 shows very little pigment. 



Larval development. — Incubation at laboratory temperature occupied approximately 

 50 hours. The newly hatched larvae (fig. 97) are approximately 3.5 mm. in length and 

 relatively slender. The head is somewhat deflected at the anterior end of the yolk sac. 



Fig. 98. — Larval fish i day after hatching, actual length 4 mm. 



Fig. 99. — Larval fish 4 days after hatching, actual length 5,2 mm. 





■.•■i^r'>^-^^i 



Fig. 100.— Young fish 30 mm. in length. 

 POMOLOBUS J-STIVALIS. 



The vent is located near the posterior end of the body. Black chromatophores occur 

 sparsely scattered over the yolk sac and in a series along the intestine. 



One day after hatching (fig. 98) the larvae have grown to a length of 4 mm. The 

 greater part of the yolk is absorbed and the head is no longer deflected. The general 

 appearance of the larva has not changed materially, although the series of chromato- 

 phores along the intestine has become more marked and a few chromatophores appear 

 at the base of the ventral-fin fold posterior to the vent. 



Four days after hatching (fig. 99) the larvae have attained a length of 5 mm. or over. 

 The yolk is completely absorbed. The distribution of pigment remains essentially as 

 in the earlier stages. 



Figure 100 illustrates a young fish 30 mm. in length. Young fish 30 to 50 mm. in 

 length, as indicated above, were present in abundance during July in the waters in 

 which adult fish were found spawning. Young fish of this size have the general appear- 

 ance of adults and show all the diagnostic characters of the species. 



