Text-book of comparative anatomy . FIG. 270.— Stage J. Section not quite median. Lettering as before. In addition : cts, cephalo-thoracic shield; ms, mesoderm segments; tgi, 1st thoracic ganglion (of 1st maxillipede); mg,inandibular ganglion. lfUJ-£ Dm Fig. 2SO.—Ripe embryo. Lettering as before, mu, Mouth ; Lm, ventral chord; wise, muscu-lature ; aa, arteria abdominalis ; as, arteria sternalis ; Id, diverticula of the mid-gut (hepatopancreas) •li, heart; pc, pericardium ; md, extensions of the mid-gut; mm, muscles of the masticatory stomach ;pk, pyloric valve. 406 COMPARATIVE ANATOMY CHAP
Text-book of comparative anatomy . FIG. 270.— Stage J. Section not quite median. Lettering as before. In addition : cts, cephalo-thoracic shield; ms, mesoderm segments; tgi, 1st thoracic ganglion (of 1st maxillipede); mg,inandibular ganglion. lfUJ-£ Dm Fig. 2SO.—Ripe embryo. Lettering as before, mu, Mouth ; Lm, ventral chord; wise, muscu-lature ; aa, arteria abdominalis ; as, arteria sternalis ; Id, diverticula of the mid-gut (hepatopancreas) •li, heart; pc, pericardium ; md, extensions of the mid-gut; mm, muscles of the masticatory stomach ;pk, pyloric valve. 406 COMPARATIVE ANATOMY CHAP. Development of the eye.—Each eye consists of three elements : (1) a hypodermallayer, (2) an ectodermal imagination, and (3) a nerve mass. The hypodermal layer becomes many-layered ; some of its elements combine toform groups, each of which consists of 8 cells, 4 of which (Sempers cells) secrete acuticular corneal facet, while the 4 others produce the crystalline cone. The ectodermal invagination (optic fold) deepens in the Nauplius stageand is constricted off in stage (G) as a solid mass of cells. This mass developsinto a fold, opens outward and upward, with an outer and inner wall several layersthick. The outer wall becomes conne
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
