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AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



Fig. 39. AMPHIOXUS, reduced. Transverse sections through regions of 

 A, olfactory pit ; B, buccal cavity ; C, pharynx and liver; D, atriopore; 

 E, anus. All enlarged to same scale. Lymph-spaces dotted. R and 

 L, right and left sides, a.f, Anal fin; an, anus; at, atrial cavity 

 (atriopore shown diagrammatically in D) ; b. c, buccal cavity (just 

 beginning in A); b.sk, pieces of buccal skeleton (others seen within 

 sections through buccal cirri) ; c.ao, cardiac aorta; c<e, sections of 

 coelom ; cr, buccal cirri; d, dermis; d.ao, dorsal aorta; d.ar, dorsal 

 artery; d.f, dorsal fin; d.gr, dorsal groove of pharynx; d. n, dorsal 

 nerve ; en, endostyle ; ep, epidermis ; ex, excretory tube (brown tube 

 of Lankester) ; f.r, fin ray; g, possible gustatory organ; h.v, hepatic 

 veins; in, intestine; I, liver; l.f, lateral fin; ///, lymph-spaces; m, 

 myomeres and (in B) mouth; m.c, metapleural lymph-canal; my, 

 myoccele, including fin-ray spaces and (in A) spaces connected with 

 myomeres; n, notochord, the dots represent nuclei around it is 

 seen its sheath (left white) continued into septa and neural sheath; 

 n.c, nerve cord; nv, nerves (in A); o, eye; ol, olfactory pit; ov, ovary; 

 p.v, portal veins; sp, septa; tr.m, transverse muscles; v.n, ventral 

 nerve (represented as coming off too high up). 



