closure of the blastopore), middle (blastopore clo- 

 sure to tail separation), and late (tail separation to 

 hatching). 



Early Stage 



During this stage, eggs were distinguishable by 

 measurement of egg and oil globule diameters. 

 The yolk occupied about 81'7r of the egg diameter. 

 It appeared translucent and yellow-to-amber in 

 color with transmitted, incandescent light. With 

 closure of the blastopore the embryo encompassed 

 about half the circumference of the yolk. 



Middle St.igc 



Faint melanophores began to appear on the dor- 

 sal surface of the embryo (F'igure la). They were 

 widely spaced, appeared randomly distributed, 

 and were easily overlooked at magnifications 

 under 50 x. No pigment was noted on either the 

 yolk or oil globule. Myomeres ( 12-22) became visi- 

 ble but were difficult to count with any accuracy. 

 The optic vesicles became clearly visible but 

 lacked pigment. By the end of this stage the 

 number of melanophores increased although they 

 were still present only on the dorsum. In some eggs 

 they began to appear more numerous just behind 

 the head while a few developed on the occiput. As 

 the tail developed free of the yolk material, traces 

 of finfold became visible on the posterior edge of 

 the embryo. 



Laif Stage 



Melanophores enlarged so they became clearly 

 visible (Figure lb). Some developed along the 

 sides and in some cases a few were noted on the 

 yolk near the embryo. Melanophores along the 

 dorsum commonly migrated into a more or less 

 straight middorsal row extending from the nape to 

 the tip of the tail. As the embryo developed, the 

 portion of this line of pigment posterior to the vent 

 migrated into the dorsal finfold while the lateral 

 melanophores migrated into the ventral finfold 

 (Figure Ic). As this occurred, little pigment re- 

 mained on the trunk except for the anterior por- 

 tion of the middorsal row. Numerous small dots 

 persisted on the nape and dorsal surface of the 

 head. Once melanophores had migrated into the 

 finfold they began to coalesce into four distinct 

 spots — two in the dorsal and two in the ventral 

 finfolds; the dorsal pair aligned above the ventral 



pair. An additional group of melanophores aggre- 

 gated ventrally near the tip of the notochord (Fig- 

 ure Id). Much of this pigment spot appeared to be 

 in the finfold but it was always in contact with the 

 trunk and often extended upon it. Some of the 

 small melanophores remaining on the anterior 

 dorsum coalesced and moved into the dorsal finfold 

 approximately midway between the vent and 

 head. In some embryos a portion of the finfold 

 melanophores became dendritic before they 

 coalesced. 



The oil globule was located posteriorly in the 

 yolk near the developing vent where it remained 

 through hatching. In some advanced, late stage 

 eggs, one or two melanophores formed on the sur- 

 face of the oil globule. No additional pigmentation 

 developed on the yolk. Shortly before hatching the 

 embryo encircled the yolk with the tip of the tail 

 almost reaching the snout. 



De^cnptKin ol Early Larvae 



Two recently hatched larvae measured 1.4 mm 

 NL (notochord length! and were essentially 

 identical to advanced late stage embryos. Three 

 dark spots were present near the margin in the 

 dorsal finfold, two near the margin in the ventral 

 finfold, and one along the ventral body margin 

 near the tip of the notochord. Small melanophores 

 were scattered over the dorsum from the occiput to 

 a point about halfway to the tip of the tail. The 

 eyes remained unpigmented. The oil globule was 

 located at the posterior edge of the yolk sac. 



By 2.0 mm NL (Figure 2a) no change in pig- 

 mentation had occurred. The yolk was reduced in 

 size by about 50'* and the gut and vent more 

 clearly defined. 



Specimens 2.0 mm NL were obtained from 

 preserved plankton samples where the finfold and 

 its pigmentation were frequently lost. Between 

 2.1 and 2.3 mm NL (Figure 2b) the yolk sac was 

 fully resorbed, eye pigmentation developed, and 

 larvae developed many of the characteristics de- 

 scribed by Richardson and Joseph ( 1973) for 2.3- 

 2.5 mm larvae. Melanophores developed along the 

 ventral body margin from the gut to the pro- 

 nounced spot near the tip of the notochord. As 

 these melanophores developed, most or all of the 

 pigmentation on the dorsum was lost. The distinc- 

 tive markings in the dorsal and ventral finfolds of 

 yolk-sac larvae remained with the exception of the 

 posterior dorsal spot. This spot was either lost as 

 the caudal band, described by Richardson and 



710 



