DEVELOPMENT OP THE SKULL IN THE SALMON. 
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PLATE II. 
First Stage (continued). 
Fig. 1. Section, through the eyes, of an unsymmetrical embryo. x24 diameters. 
Fig. 2. Another similar section, further back, x 24 diameters. 
Second Stage. — Embryos with hyoid arch split up. 
Fig. 3. Under view of head, somewhat depressed, x 24 diameters. 
Fig. 4. Under view of same head, with postoral arches removed. X 24 diameters. 
Fig. 5. Part of another skull, x 30 diameters. 
Third Stage. — Mandibular arch segmented. 
Fig. 6. Lower view of skull and face, with branchial arches removed, x 24 diameters. 
Fig. 7. Same object, upper view. X 24 diameters. 
Fig. 8. Branchial arches of same, separately shown, from below. X 24 diameters. 
Fourth Stage. — Head emerging from the chorion, and hatched embryos. 
Fig. 9. Front view of head. X 20 diameters. 
Fig. 10. Section of the same, through the eyes. x20 diameters. 
Fig. 11. Upper view of head. Xl0 diameters. 
PLATE III. 
Fourth Stage (continued). 
Fig. 1. Side view of head, with face dissected. x25 diameters. 
Fig. 2. Lower view of same, dissected, x 25 diameters. 
Fig. 3. Section of head of partly hatched embryo, x 20 diameters. 
Fig. 4. Side view of head of hatched embryo. X 20 diameters. 
Fig. 5. Section of the same. X 20 diameters. 
Fig. 6. Primordial skull of same, from above. X 25 diameters. 
Fig. 7. Section of ripe embryo-head through nasal sacs. X 25 diameters. 
Fig. 8. Another section through prosencephalon. X 25 diameters. 
Fig. 9. Another through the same, and also the eyeballs. X 25 diameters. 
Fig. 10. Another section, behind the eyes, x 25 diameters. 
Fig. 11. Another section, behind the left ear-sac. x25 diameters. 
MDCCCLXXIII. 
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