GIBSON — CEPHALOCHOEDA : " AMPHIOXIDES. 



255 



EXPLANATION OE PLATE 15. 



a. Atrium. 

 ao. Aorta. 

 b.a. Branchial artery, or its anterior 



continuations. 

 b.c. Buccal cavity. 

 c.c. Ccfilomic canal. 

 c.ff. Club-shaped gland. 

 d.s. Dorsal stomocoele. 



e. Endostyle {d. dorsal, v. ventral limb). 

 e.c. Epibranchial coelom. 

 e g. Epibranchial groove. 



g. Gonad. 

 H.p. Hatschek's pit. 

 h.c. Hypobranchial ccelom. 

 i.l.c. Inner lip-cavity. 

 I.e. Lymph-canal, probably derived from 

 ventral rostral cavity. 

 l.r.c. Lateral rostral canal. 

 m.a. Anterior mouth-muscle. 

 m.b. Branchial muscle. 

 m.p. Posterior mouth-muscle. 

 m.jM. Muscle of pre-oral organ. 



m.pt,. Pterygial muscle. 

 m.o. Outer lip-muscle. 

 mtp.r., tntp.l. Bands of clear cells on right and 

 left metapleurcs. 

 n.H. Hatschek's nephridium. 

 n.l. Excretory tubule of left series. 

 n.r. Possible excretory tubule of right series. 

 o.l.c. Outer lip-cavity. 

 o.p. Olfactory pit. 

 pc. Pterygoccele. 



ph. Anterior diverticulum of pharynx. 

 p.g. Pre-oral gut. 

 p.o.v. Pre-oral organ, ventral portion. 

 p.r.,p.l. Right and left peripharyngeal bands. 

 r.o. Raderorgan. 

 r.c. Ventral rostral canal. 

 s.c. Splanchnocoele. 

 S.7- c. Subdorsal rostral canal of Goldschmidt. 

 sk. Skeletal lamella. 

 st. Stomodaeum. 

 v.r.c. Ventral rostral cavity. 

 vc. Velicavum. 



FJE 



Fig. 



Fig. 

 Fiff. 



1. Amphioandts pdagicus, 9 mm. long, seen from the left. (The fin-strands of the tail should be 



finer and more numerous. The (fallacious) appearance of fin-ray boxes, at x , is somewhat 

 exaggerated.) 



2. Metamorphosed animal, 8 mm. long, seen from the right (buccal cirrhi omitted). 



3. Head of normal A. pelagicus, from tlie left. 



4. Head of a large specimen of A. pelagicus, showing widely open pre-oral organ, mouth, and 



gill-slits. 



Figs. 5-1 1. Transverse Sections of A., pelagicus. 



Fig. .5. Through anterior region of pre-oral organ, showing Hatschek's pit. 



Fig. 6. Through mid-region of pre-oral organ. 



Fig. 7. Through extreme posterior end of pre-oral organ, just in front of mouth-opening. 



Fig. 8. Through mouth, a little in front of mid-region. 



Pig. 9. Through mouth, behind 1st gill-slit. 



Fig. 10. Between 14th and 15th gill-slits. 



Fig. II. Behind 37th (last) gill-slit. 



Fig. 12. Transverse section through 10th gill- slit of A. valdivia, showing excretory tubule. 



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