THK DEVELOPMENT OF SYMBIIANCHUS MARMORATUS. 49 
EXPLANATION OF PLAICES 1—4. 
Illustrating Miss Monica Taylor’s paper on “The Develop- 
ment of Sy mb ranch us.” 
PLATE 1. 
Fig. 1. — A surface view of the youngest stage in the collection. The 
segmenting blastoderm looking like a white circular pad “ let into ” the 
yolk-mass occupies the centre of the flattened pole of the egg. 
Fig. 2. — An egg of Stage 10. The blastoderm has a thickened rim, 
and at one point this rim becomes accentuated to form the embryonic 
rudiment. 
Fig. 3. — An egg of Stage 11. 
Fig. 4. — An egg of Stage 17. 
Fig. 5. — An egg of Stage 21. o. v. Optic vesicles, p./. Pectoral fins. 
V. r. Rudiment of visceral arches with their nerve supply. 
Fig. 5a.— An egg of Stage 21, fixed in corrosive acetic, b. r. Branchial 
rudiment, h. a. Hyoid arch. m. a. Mandibular arch. o. v. Optic vesicles, 
p. /. Pectoral fins. 
Fig. 6. — An egg of Stage 22. 
Fig. 7. — An embryo of Stage 23. c. s. Cartilaginous skeleton of 
pectoral fin. e. Eye. m. Mesencephalon, o. Otocyst. r. c. Rhomben- 
cephalon. r. Rostrum. 
Fig. 8. — Side view of an embryo of Stage 24. e. Eye. n. Nostril. 
0 . Otocyst, 
Fig. 9. — Larva of Stage 26. a. Anus. c. r. Cerebellum rudiment, e. 
Eye. li. Heart, n. Olfactory organ, o. 1. Optic lobes, ojp. Operculum, 
s. i. V. Subintestinal vein. 
Fig. 10. — A larva of Stage 30. s. ^. v. Subintestinal vein. y. Yolk. 
Fig. 11. — Sagittal section through an embryo of Stage 25. i. Inner 
and 0 . outer layer of ectoderm, e. Epiphysis, m. Mesencephalon, pc. 
Pericardium, p. Prosencephalon, r. Rhombencephalon, v. Ventricle. 
PLATE 2. 
Fig. 12. — Right pectoral fin and shoulder girdle of a larva of Stage 30. 
Fig. 13. — A larva of Stage 32. s. ^. v. Subintestinal vein. y. Yolk. 
VOL. 59, PART 1. NEW SERIES. 4 
