Figs. 8a and 8b. View from the ventral surface and from the side of an embryo, after the ventral flexure has considerably advanced.
Fig. 9. Somewhat older embryo, viewed from the ventral surface.
[Plates 31] and [32].
Complete List of Reference Letters.
ao. Aorta. ab.g. Abdominal nerve cord. ch. Cheliceræ. ch.g. Ganglion of cheliceræ. ep. Epiblast. hs. Hemispherical lobe of supra-œsophageal ganglion. ht. Heart. l.l. Lower lip. m. Muscles. me. Mesoblast. mes. Mesenteron. mp.g. Malpighian tube. ms. Mesoblastic somite. œ. Œsophagus. p.c. Pericardium. pd. Pedipalpi. pd.g. Ganglion of pedipalpi. pr. Proctodæum (rectum). pr.c. Primitive cumulus. s. Septum in abdomen. so. Somatopleure. sp. Splanchnopleure. st. Stomodæum. su. Suctorial apparatus. su.g. Supra-œsophageal ganglion. th.g. Thoracic ganglion. v.g. Ventral nerve cord. y.c. Cells derived from yolk. yk. Yolk. y.n. Nuclei of yolk cells.
Ig—IVg. Ganglia of ambulatory limbs. 1—16. Postoral segments.
Fig. 10. Section through an ovum, slightly younger than fig. 1. Shewing the primitive cumulus and the columnar character of the cells of one half of the blastoderm.
Fig. 11. Section through an embryo of the same age as fig. 2. Shewing the median thickening of the blastoderm.
Fig. 12. Transverse section through the ventral plate of a somewhat older embryo. Shewing the division of the ventral plate into epiblast and mesoblast.
Fig. 13. Section through the ventral plate of an embryo of the same age as fig. 3, shewing the division of the mesoblast of the ventral plate into two mesoblastic bands.