FISHERY BULLETIN: VOL. 81, NO 4 



lens was not bulging out of the cup. In most 

 specimens, one or two large oil droplets were near the 

 cephalic region. Embryos extended slightly more 

 than one- half way around the yolk (Fig. 3 A). 



At 302.0 h (12.6 d), the divisions of the brain were 

 more clearly differentiated. The mid- and hindbrains 

 had increased in size. Lens of the eye protruded from 

 the optic cup. Otic vesicles, Kupffer's vesicle, pec- 

 toral buds, and notochord were present. Toward the 

 caudal end of the embryo, clearly distinguishable 

 somites were first observed and ranged in number 

 from 12 to 14. The embryo reached about two- thirds 

 way around the yolk (Fig. 3B). 



Embryos in the tail- free stage were first noted at 

 424 h (17.7 d). Kupffer's vesicle was deeper. The 

 olfactory placode was visible. Somites had increased 

 in number to 16 or 17. The embryos stretched about 

 three- fourths way around the yolk (Fig. 3C). 



Late embryogenesis: Darkly pigmented eyes were 

 first visible at 472.0 h(19.7 d). All observed embryos 

 had dark eyes and a pulsating heart by 520.0 h (21.7 

 d). Lens of the eye was large. Head was large and 

 rather flattened. Brain ventricles were apparent in 

 dorsal view. Otoliths were present. The rudiment of 



the lower jaw was visible. Pectoral fins were spread 

 over the yolk sac. Finfold was apparent. Tip of the tail 

 was curved around past the mouth. There were about 

 25 somites. Most specimens had a single large oil 

 globule located beneath the head (Fig. 3D, E). 



Embryo movement within the eggs was first ob- 

 served at 545.0 h (22.7 d). The tail passed well over 

 the hindbrain on the lateral flexion. The lower jaw 

 became more developed, but the mouth was not yet 

 open. Opercular margin was well defined. The anal 

 vent was visible. The circulatory system became 

 functional along the length of the tail; this was first 

 noted at 800.0 h (33.3 d), and all observed embryos 

 had noticeable circulation by 825.0 h (34.4 d). 



Prehatching stage: Embryos in this stage were 

 characterized by silvered eyes and by the onset of 

 pigmentation of the body. Most embryos were in this 

 stage at about 850.0 h (35.4 d). Contracted 

 melanophores densely covered the dorsal surface of 

 the yolk sac. A few large stellate melanophores were 

 present behind the head. Evenly spaced melano- 

 phores were present from near the vent along the 

 ventral line of the tail. Yolk sac was much reduced in 

 size. Tail was wrapped about \ l h times around the 



FUJI RK 3. — Later development of the eggs of the longhorn sc\i\pm,Myoxocephalux octndcci'mspinosun, artificially propagated in the laboratory: 

 A-C) middle embryonic stages, 2.16 mm (250-424 h); D-E) late embryonic stage,-, 2.16 mm (578-780 h); F) prehatch stage, 2.18 mm (880 h); 

 scale = 0.5 mm. Measurements refer to mean egg capsule diameters. 



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