Fig. 43. — Sagittal section of a young scorpion (arachnid) to be compared with 

 fig. 44. c. a, carotid artery; ch, cereliral hemispheres; e. t, parietal eye tube; 

 ht^-hP, heart; I. e. g, lateral eye ganglion; inxl, maxillaria; m, mouth; nch, noto- 

 chord; oc.r, occipital region; pne.g, parietal eye ganglion; ro, rostrum; st.co, 

 stomodaeal commissure. (After Patten's " Evolution of the Vertebrates and their 

 Kin " [P. Blakiston's Sons and Co.].) 



Fig. 44. — Sagittal section of a primitive vertebrate embryo, showing the rela- 

 tion of its principal organs to those in the arachnids (cf. fig. 43); schematic, a. np, 

 anterior neuropore; h. nv, belly navel; chl, cerebellum; C. d, duct of Cuvier; 

 ch, cerebral hemispheres; cnv, new ventral mouth; et, eye tube; hy, hyoid; I, lung; 

 TO, mouth; oe, cesophagus; ocr, occipital region; ol. I, olfactory lobe; op. I, optic 

 lobe; pa. e, parietal eye; pit, pituitary body; pr. mx, premaxilla; ■)nd, mandible; 

 mx, maxilla; .S', stomach; s. v, sinus venosus; v, ventricle. (From Patten's " Evolu- 

 tion of the Vertebrates and their Kin " [P. Blakiston's Sons and Co.].) 



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