DESCRIPTION OF FIGURES 1-8, PLATES 1-15

The word "Plate" refers to the physical pages on which the Figures were printed. The word is not used as an illustration identifier. The complete caption text from this section has been added to each Figure. In the original, Figures were labeled only with number and letter. Based on the author's age at time of publication, "Miss C. M. Reese" is more likely to have been his sister than his daughter.

The surface views were drawn, under the author's direction, by Miss C. M. Reese. The first two of these views were copied, by permission, from S. F. Clarke; the others were drawn from the specimens themselves.

All of the figures of any one stage are given the same number, followed by distinguishing letters, so that it is possible to tell at a glance what figures belong together.

All of the figures except those from Clarke were drawn under a camera lucida.

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

[Figure 1A.] A sagittal section of an embryo of approximately the age of the one shown in figure 1. × 43.

[Figure 2.] A dorsal view of an embryo with five pairs of mesoblastic somites.

[Figure 2A.] A sagittal section of an embryo of the stage shown in figure 2. × 43.

[Figure 2B.] A transverse section through the headfold of an embryo of the stage shown in figure 2. × 43.

[Figure 3.] A dorsal view of an embryo with about fifteen pairs of somites. × 20.

[Figures 3A]-[3D]. A series of transverse sections through an embryo of the stage of the one shown in figure 3. × 43.

[Figure 4.] A surface view of an embryo with about twenty pairs of somites. × (about) 15.

[Figures 4A]-[4D]. A series of transverse sections through the anterior end of an embryo of the approximate age of the one shown in figure 4. × 20.

[Figures 4E] and [4F]. Two transverse sections through the thyroid gland of this stage; more highly magnified. × 102.

[Figures 4G]-[4M]. A series of transverse sections caudad to the preceding. Figure 4H, × 43; other figures, × 20.

[Figure 5.] A surface view, in profile, of an embryo at the time of the origin of the limbs. × (about) 5.

[Figures 5A]-[5I]. A series of transverse sections through an embryo of the age shown in figure 5. × 7.

[Figure 5J.] A composite drawing of reconstructions of the enterons of two embryos of the age of the one shown in figure 5. One reconstruction was in wax, from sagittal sections, the other was a plotted reconstruction from transverse sections. × 14.

[Figure 6.] A surface view, in profile, of an embryo with well developed manus and pes. × (about) 5.

[Figure 6A.] A reconstruction, plotted from transverse sections, of the enteron of an embryo of about the age of the one shown in figure 6. × 14.

[Figures 6B]-[6H]. Part of a series of transverse sections from which the preceding reconstruction was made. × 7.

[Figure 7.] A reconstruction of the enteron of an embryo of 42 mm. crown-rump length.

[Figures 7A]-[7G]. A part of the series of transverse sections from which the preceding reconstruction was made. × 7.

[Figure 7H.] A high power drawing of a portion of the wall of the oesophagus in the region of figure 7A. × 190.

[Figure 7I.] A high power drawing of a portion of the wall of the stomach in the region of figure 7C.

[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. g^1-5, gill clefts. gf^1-6, 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.

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

Fig. 2. A dorsal view of an embryo with five pairs of mesoblastic somites.

Fig. 2a. A sagittal section of an embryo of the stage shown in figure 2. × 43.

Fig. 2b. A transverse section through the headfold of an embryo
of the stage shown in figure 2. × 43.

Fig. 3. A dorsal view of an embryo with about fifteen pairs of somites. × 20.


Fig. 3a.	Fig. 3b.
4
Fig. 3c.	Fig. 3d.
A series of transverse sections through an embryo of the stage of the one shown in figure 3. × 43.

Fig. 4. A surface view of an embryo
with about twenty pairs of somites. × (about) 15.


Fig. 4a.	Fig. 4b.

Fig. 4c.	Fig. 4d.
A series of transverse sections through the anterior end of an embryo of the approximate age of the one shown in figure 4. × 20.

Fig. 4e.	Fig. 4f.
Two transverse sections through the thyroid gland of this stage; more highly magnified. × 102.


Fig. 4g.	Fig. 4h.	Fig. 4k.

Fig. 4i.

Fig. 4j.	Fig. 4l.	Fig. 4m.
A series of transverse sections caudad to the preceding. Figure 4H, × 43; other figures,× 20.

Fig. 5. A surface view, in profile, of an embryo
at the time of the origin of the limbs. × (about) 5.


Fig. 5a.	Fig. 5b.	Fig. 5c.
8
Fig. 5d.	Fig. 5e.	Fig. 5f.

Fig. 5g.	Fig. 5h.	Fig. 5i.
A series of transverse sections through an embryo of the age shown in figure 5. × 7.

Fig. 5j. A composite drawing of reconstructions of the enterons of two embryos of the age of the one shown in figure 5. One reconstruction was in wax, from sagittal sections, the other was a plotted reconstruction from transverse sections. × 14.

Fig. 6. A surface view, in profile, of an embryo
with well developed manus and pes. × (about) 5.

Fig. 6a. A reconstruction, plotted from transverse sections, of the enteron of an embryo of about the age of the one shown in figure 6. × 14.


Fig. 6b.		Fig. 6c.
11
Fig. 6d.	Fig. 6e.		Fig. 6f.

Fig. 6g.		Fig. 6h.
Part of a series of transverse sections from which the preceding reconstruction was made. × 7.

Fig. 7. A reconstruction of the enteron of an embryo of 42 mm. crown-rump length.


Fig. 7a.	Fig. 7b.
13
Fig. 7c.	Fig. 7d.

Fig. 7e.	Fig. 7f.
14
Fig. 7g. A part of the series of transverse sections from which the preceding reconstruction was made. × 7.


Fig. 7h. A high power drawing of a portion of the wall of the oesophagus in the region of figure 7A. × 190.	Fig. 7i. A high power drawing of a portion of the wall of the stomach in the region of figure 7C.

Fig. 7j. A high power drawing of a portion of the wall
of the duodenum in the region of figure 7D.

Fig. 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.