Development of the Digestive Canal of the American Alligator

by A. M. Reese

[Figure 7J.] A high power drawing of a portion of the wall of the duodenum in the region of figure 7D.

[Figure 8.] An outline drawing, from the ventral aspect, of the enteron of an embryo of 20 cm. length, at about the time of hatching; made from a dissection. × 1.

Lettering for all Figures

a, head-fold of amnion. aa, anterior appendage. ac, anterior cardinal vein. aip, anterior intestinal portal. al, allantois. an, anterior nares. ao, aorta. ar, aortic arch. au, auricle. b, bulbus arteriosus. bc, body cavity. bd, bile duct. bd´, opening of bile duct to liver. bd´´, opening of bile duct to duodenum. blp, blastopore. bp, basilar plate. bs, bile-sac. bv, blood vessel. c, centrum of vertebra. ca, caudal artery. ce, caecum. ch, cerebral hemisphere. cl, cloaca. cm, circular muscle layer. cn, cranial nerve. cp, posterior choroid plexus. cv, cardinal vein. d, duodenum. dc, ductus Cuvieri. di, diverticulum of stomach. e, eye. ec, ectoderm. ec´, thickening of ectoderm. en, entoderm. en´, endocardium. ent, enteron. ep, epidermal layer of ectoderm. ep´, epithelium. epi, pineal body. es, embryonic shield. f, fronto-nasal process. fb, forebrain. fg, foregut. g1-5, gill clefts. gf1-6, gill folds. gl, glomerulus. h, head-fold. gs, glottis. gz, gizzard. hb, hindbrain. hc, head cavity. hg, hindgut. ht, heart. i, intestine. i´, stomach. il, large intestine. in, infundibulum. io, intromittent organ. ir, iris. it, iter. k, kidney. la, larynx. li, liver. lm, longitudinal muscle layer. ln, lens. lp, lp´, etc., loops of intestine. lu, lungs. lv, lens vesicle. m, mouth. ma, manus. mb, midbrain. me, medullary canal. me´, tip end of medullary canal. md., mandibular folds.

mes, mesoderm. mes´, myocardium. mf, medullary fold. mg, medullary groove. mk, Meckel's cartilage. ml, muscle layer. mp, muscle plate. ms, mesentery. mv, meatus venosus. mx, maxillary fold. myc, myocoel. n, nasal cavity. na, neural arch of vertebra. nc, neurenteric canal. nl, nervous layer of ectoderm. nt, notochord. o, ear vesicle. oc, optic cup. oe, oesophagus. on, optic nerve. os, optic stalk. ov, optic vesicle. p, pituitary body. pa, posterior appendage. pag, post-anal gut. pan, pancreas. pan´, opening of pancreas. pc, posterior cardinal vein. pe, pes. pg, primitive groove. ph, pharynx. pip, posterior intestinal portal. pl, pelvis. pn, posterior nares. pr, pericardial cavity. ps, primitive streak. pt, pecten. py, pylorus. r, rib. rt, retina. s, somites. sc, spinal cord. se, spenethmoid cartilage. sg, spinal ganglion. sl, submucosa. sm, splanchnic mesoblast. sn, spinal nerve. so, somatic mesoblast. st, stomodaeum. sy, sympathetic nervous system. t, tail. ta, trachea. tg, thyroid gland. tn, tongue. to, tooth anlage. tr, trunchus arteriosus. tv, tv´, third ventricle of brain. ty, thymus gland. u, umbilical stalk. v´, v´´, v´´´, first, second, and third cerebral vesicles. va, vascular area. vc, vocal cords. vm, vitelline membrane. vn, ventricle of heart. vp, velum palitum. vv, vitelline blood vessels. wd, Wolffian duct. wdo, opening of Wolffian duct. wr, Wolffian ridge. wt, Wolffian tubule. x, point of origin of bronchi. y, yolk. ys, yolk-stalk.

1

Fig. 1. A surface view of an embryo, from the dorsal aspect, at the beginning of the formation of the enteron.

Fig. 1a. A sagittal section of an embryo of approximately the age of the one shown in figure 1. × 43