60 Normentafeln zur Entwicklungsgeschichte der Wirbeltiere. 
of the trigeminal nerve by a short ganglionic commissure. From the anterior edge of this commissure there 
projects forward a small filament, the superficial ophthalmic ramus of the trigeminal nerve (R.oph.sup.V). 
It extends ventrally from the mesocephalic ganglion nearly to the roof of the diencephalon. Both the 
mandibular and maxillary rami of the trigeminal nerve (R.md.V; Rm.x.V.) extend to the base of the first gill 
arch. In the reconstruction they are represented as cut off about the middle of their course. The facial 
complex presents several features decidedly different from those seen in the preceding reconstruction of an 
embryo 15 mm. in length. The superficial ophthalmic ramus (R.sup.oph.VII) extends forward to the anterior 
border of the mid-brain. The buccal ramus (R.buce. VII), the ganglion but not the nerve of which was present 
in the preceding embryo, now extends to the base of the first arch. The epibranchial ganglion (G.epib. VLI) 
is well marked and the hyoid ramus (R.hyo.VII) extends to the base ofthe second arch. The acoustic nerve 
(N.ac.) needs no special description. The abducent nerve (N.ab.) is entirely covered by the facial complex 
and by the otocyst and is represented in dotted lines in the figure. It springs by three roots from the floor 
of the hind-brain mesial to the otocyst. This structure (Oto.) is somewhat broader in proportion to its length 
than was the otocyst in the preceding reconstruction. The sacculus (Sac.) is represented by a large ill 
defined pouch in the floor. The glossopharyngeal nerve shows no feature of special interest aside from 
the well established epibranchial ganglion (G.epib. IX). The first three epibranchial ganglia of the vagus 
are clearly established and the corresponding branchial rami extend about half way down their respective 
arches. The lateral line ramus (R.lat.X) extends backward to the level of the duodenum, but in the figure 
it is represented as cut off near its origin from the ganglion. The visceral ramus (R.vis.X) extends backward 
to the anterior end of the stomach. The spinal — occipital ganglia are represented by two enlargements of 
dorsal ganglionic commissure (Comm.d.) which connect the ganglion to the vagus with the first spinal 
ganglion. The motor roots of the spinal — occipital nerves are well developed, but are not connected with 
the ganglia (G.sp.oc). The first fifteen spinal ganglia are represented in the reconstruction. They are all 
connected by the dorsal ganglionic commissure, although in a younger embro I5 mm. in length, which is 
represented in Fig. 13, this ganglionic commissure is broken down in the anterior part of the trunk region. 
The sympathetic ganglia (Symp.) are seen as small oblong or spherical masses lying on the mesial surface 
of the spinal nerves at the level of the dorsal aorta. 
All six gill slits now open to the pharynx. The thyreoid (7h.) lies below the second slit and is 
connected with the floor of the pharynx only by a slender cord. The hypophysis (Hyp.) extends forward 
and covers the anterior part of the infundibulum. Its connection with the pharynx is somewhat constricted. 
The distal portion is expanded and divided by shallow grooves into an anterior and two lateral lobes. 
Posteriorly the pharynx is very abruptly constricted to form the oesophagus which is dilated in turn, 
forming the long cylindrical stomach ($%.). The duodenum (Duo.) is bent downward at an angle of nearly 
90° to the stomach, and also somewhat to the left. A slight constriction marks the boundary between 
these two structures. The vitelline duct (D.vit.) now opens to the intestine almost entirely in the right side. 
There is a small diverticulum in the duct just before its entrance into the intestine. The pancreas (Panc.) 
is somewhat lobulated; a ventral and posterior portion which probably represents the head of the adult 
organ being particularly prominent. The liver (L.) is represented as sectioned in the median line. The 
gall bladder (G.bl.) lies ventral to the posterior portion of the liver and is covered on its ventral surface 
by a layer of peritoneum. It is connected by a short broad cystic duct with the dilated distal end 
of the ductus choledochus (D.chol.). This dilatation also receives four hepatic ducts, three of which 
are represented in the figure. The ductus choledochus joins the duodenum on the right side just 
anterior to the entrance of the vitelline duct. The Wolffian duct (W.d.) arises from the body cavity by 
a long shallow groove, from the anterior end of which project upward two small funnels, the remains 
nt 
