266 s. WATASE 



dorsal lobe aud T'. L., the ventral lobe of tlie caudal fin (tLe latter cousisliug of 

 two halves). 



Fig. 8. Tail fiu of a gold-fish, with a shallow groove aloug its ventral margin. 

 Letters as in figs. 1 and 2. C, the paired portion of the tail-fin. 



Fig. 9. Ventral view of the same. B, the ventral groove. > ■ 



Fig. 10. Penultimate vertebra of Cypriuus carpio. 



u.a., neural arch ; v.c, vertebral centrum ; h.a., haemal arch. 



h.s., haemal spine. 



Fig. lOrt. The same of a gold-fish with tri-lobed caudal fin. /(. s. occurs in a 

 pair. Enlarged. 



Fig. 11. The last vecoguizable vertebral centrum of Cyprinus carpio. Lateral 

 view. Lv.c. centrum; /., lancet-shaped spine; ?/., urostyle; e., 5th hypural bone. 



Fig. 11a. The same of a gold-fish with trilobed caudal-fin. Enlarged, e' 

 and e' correspond to e of fig. 11. 



Fig. 12. The 1th. hj'pural bone of Cyprinus carpio, corresponding to (/. of 

 Fig. 6. Vertical (a) aud lateral (b) views. 



Fig. 13. The same of a gold-fish. Enlarged. Vertical (a) and lateral {b) 

 views. 



Fig. 14. Normal tail-fin of Cypriuidae, with two lobes a and b. 



Fig. 15. Four-lobed («, a', b, and b') tail-fin of a gold-fish. 



Fig. 16. Three-lobed tail-fin of a gold-fish. 



Fig. 17. Transverse section through the region of normal aual-fiu diagram- 

 atically represented, i.s., iaterhaemal spine; n. bony nodule; f.r., fin ray. 



Fig. 18. Transverse section through the same region of a gold-fish with 

 distinctly paired anal-fins. Diagramatic. i'. s'., interhaemal bones ; n', bony 

 nodules ; f.'v'. fin rays. 



Fig. 19-23. Diagramatic figures (transverse sections) showing the topogra- 

 phical arrangement of the caudal skeleton in different forms of the tail. s.c, 

 spinal chord, u., u', The two halves of the urostyle, intercepting the notochord. 



PLATE XX. 



Fig. 24. A young gold-fish, 13 mm. long. An, anus. The preaual fold 

 (p. a. f.), the anal fin [A) and the caudal fin (C) are in unpaired condition. Lines 

 drawn tlirough the roots of various appendages on both sides of the body con- 

 verge behind the ventral fins aud unite altogether at the beginning of the preanal 

 fold. 



Fig. 25. A young gold-fish of the same size as the preceeding. The preanal 

 fold {p, a',f'), the anal fin [A') and the caudal fin (C) are all in paired state. 

 Lines connecting the roots of various appendages on both sides of the body run 

 separate throughout the entire body-length. 



Fig. 26. An embryo gold- 



