_ao._ Aorta. _ab.g._ Abdominal nerve cord. _ch._ Cheliceræ. _ch.g._
Ganglion of cheliceræ. _ep._ Epiblast. _hs._ Hemispherical lobe of
supra-oesophageal ganglion. _ht._ Heart. _l.l._ Lower lip. _m._ Muscles.
_me._ Mesoblast. _mes._ Mesenteron. _mp.g._ Malpighian tube. _ms._
Mesoblastic somite. _oe._ OEsophagus. _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-oesophageal
ganglion. _th. g._ Thoracic ganglion. _v.g._ Ventral nerve cord. _y.c._
Cells derived from yolk. _yk._ Yolk. _y.n._ Nuclei of yolk cells.
I_g_-IV_g_. 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.
Fig. 14. Transverse section through an embryo of the same age as fig. 5,
passing through an abdominal segment above and a thoracic segment below.
Fig. 15. Longitudinal section slightly to one side of the middle line
through an embryo of the same age.
Fig. 16. Transverse section through the ventral plate in the thoracic
region of an embryo of the same age as fig. 7.
Fig. 17. Transverse section through the procephalic lobes of an embryo of
the same age. _gr._ Section of hemicircular groove in procephalic lobe.
Fig. 18. Transverse section through the thoracic region of an embryo of the
same age as fig. 8.
Fig. 19. Section through the procephalic lobes of an embryo of the same
age.
Fig. 20_a_, _b_, _c_, _d_, _e_. Five sections through an embryo of the same
age as fig. 9. _a_ and _b_ are sections through the procephalic lobes, _c_
through the front part of the thorax. _d_ cuts transversely the posterior
parts of the thorax, and longitudinally and horizontally the ventral
surface of the abdomen. _e_ cuts the posterior part of the abdomen
longitudinally and horizontally, and shews the commencement of the
mesenteron.
Fig. 21. Longitudinal and vertical section of an embryo of the same age.
The section passes somewhat to one side of the middle line, and shews the
structure of the nervous system.
Fig. 22. Transverse section through the dorsal part of the abdomen of an
embryo of the same stage as fig. 9.