O.urtr: - 
P.urtr. 
54 Normentafeln zur Entwicklungsgeschichte der Wirbeltiere. 
Fig. II. Graphic reconstruction of an embryo 9.0 mm. in length. Normal plate series No. 23. 
(ErEr@ E14 )E>@3g} 
A somewhat simpler method of representation has been employed for this reconstruction. The 
central nervous system and the digestive tract have been left in white, except where shading was necessary 
to bring out important changes in contour. The veins have been omitted. 
The thalamic nerve crest is absent, but there is still a small urtrochlearis (C.urtr.). The trigeminal 
nerve crest (N.trig.) is much as in the preceding reconstruction, with a more distinct anlage of the meso- 
cephalic ganglion (G.mes.). The facial-acoustic (N.fa.-ac.) and glossopharyngeal (N.gl.-ph.) crests need no 
special description. There are three anlagen of branchial ganglia of the vagus (N.vag.) established. The 
first spinal-occipital ganglion is only indicated by a slight swelling of the dorsal commissure — it has no 
ventral root. The second spinal-occipital ganglion (G.sp.oc.) is well established. The ganglia and ventral 
roots of all the spinal nerves shown in the figure are in contact. 
D.endol. Comm.d. R.vis.X. 
N.trig. N.fa.-ac. Oto. | D.g-ph. N:vag. G.r.lat.X | | G.sp.oe. Awüt. 
No. 
G.mes. 
@l.s.l. TR. B.cor. V. L. @.bl. Doit. Panc. 1.9. 
Hyp. 
Op. Ls.p. Fig. ı1. 
The pharynx has the same general outline as that seen in the reconstruction of the embryo, and 
the hypophysis (Hyp.) and thyreoid (Th.) are in about the same stage of development. The four anterior 
gill slits (Gl.s.) are open in part, and the fifth gill pouch is established. The liver consists of a ventral 
pouch (Li.). The pancreas (Panc.) needs no special description. The lateral groove (L.g.) ofthe vitelline duct 
(D.vit.) extends from the liver to the anterior end of the intestine. The groove of the spiral valve (Sp.v.) 
is also well marked. 
The division of the heart into sinus venosus ($.v.), atrium (At), ventricle (V.), and bulbus (B.cor.) 
is indicate. The three anterior aortic arches are complete. The fourth and fifth are represented 
by arterial sprigs from the dorsal and ventral aortae. Only the upper part of the vitelline artery (A.vit.) 
is figured. 
The subnotocordal rod (S.r.) is seen above the aorta from the level of the vitelline artery backward. 
Fig. 12. Graphic reconstruction from sagittal sections of an embryo 11.5 mm. in length. ‘Normal 
plate series No. 24. (H.E.C. 208.) X 33. 
The general method representation of this reconstruction is similar to that of Fig. ı1, which is of the 
preceding embryo in the normal plate series. The Wolffian duct has been included in this reconstruction. 
The fore-brain vesicle is now distinctly divided into telencephalon (Telen.) and diencephalon. 
It is flexed until its original antero-posterior axis lies in the vertical plane of the head. There is a well 
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