34 Normentafeln zur Entwicklungsgeschichte der Wirbeltiere. 
29 
30 
31 
32 
Brain, and Cephalic Nerves 
nn 
Hypophysis and Infundibulum 
Cranio-caudal diameter of telencephalon almost twice vertical. Cranial end of telencephalon curved a 
little upward over diencephalon. A narrow peripheral layer of ectoglia dorsal and posterior to optic stalks. 
A few fibers in periphery of chiasma. Velum transversum 0.3 mm. in length at median line. Pinealis 
0.1 mm. in length, dilated a little distally. Posterior and superior commissures as in preceding stage (No. 26). 
Mesencephalon nearly circular in section. Walls a little thickened ventrally. A narrow peripheral zone 
of ectoglia in ventral third of walls. Hind-brain much as in preceding stage. — Distinct superficial oph- 
thalmic ramus of trigeminus arising. near root of nerve. Mandibular and maxillary rami of trigeminus 
extend to bases of respective processes. Superficial ophthalmic ramus of facial extends forward as far 
as anterior edge of fore-brain. Hyomandibular division of facial-acoustic ganglion connected with general 
mass only at anterior end. Hyoid ramus extends to base of hyoid arch. Four branchial rami of vagus. 
Lateral line ramus extends posteriorly to level of pectoral fin. 
Cranio-caudal diameter of telencephalon almost twice vertical. Walls nearly 0.2 mm. thick. Peripheral 
ectoglic layer throughout telencephalon — thinnest in anterior wall. Formation of cinerea above and 
anterior to origin of olfactory nerve. Distinct though low paraphysis. Velum transversum 0,65 mm. in 
length at median line. Anterior wall twice as thick as posterior. Walls separated by layer of vascular 
mesenchyma. Distinct postvelar arch, with walls nearly in contact. Pinealis nearly 0.3 mm. long, ex- 
tending backward over roof of diencephalon. Expanded distally. Small anterior commissure, Posterior 
commissure much larger. Ganglion habenulae differentiated. Differentiation of cinerea in ventral zone 
of mesencephalon. Tractus habenulo-peduncularis differentiated? A distinct bundle of fibers (tractus 
olfactorius habenularis?) pass from superior commissure ventrally and posteriorly half way to the optic 
chiasma. Fasciculus longitudinalis posterior can be traced throughout greater part of medulla. Tractus 
ascendens trigemini extends forward 200 u anterior to origin of nerve. Tractus descendens can be traced 
| posteriorly to .origin of facial nerve. — Trochlearis present; extends downward beyond base of mes- 
encephalon. Divisions of facial-acoustic ganglion only connected at origin of ganglion. Lateral line 
ramus of vagus extends posteriorly almost to caudal fin. 
Telencephalon much expanded laterally. Lateral walls at level of origin of olfactory nerve 0.3 mm. thick. 
Choroid plexus indicated by two distinct but small folds — a few mesenchymal cells between walls of 
folds. Cinereal layer throughout walls of telencephalon. Pinealis 0.5 mm in length (by sections). Lumen 
of stalk occluded at base for 50 u (by sections). Cerebellar anlagen much thickened on either side of 
median line with formation of cinerea. Lobus lineae lateralis forms a distinct projection of the inner wall 
of hind brain; bounded ventrally by a shallow groove. A very slight longitudinal groove separates the 
fasciculus longitudinalis medialis and lobus visceralis. Differentiation of reticularis throughout medulla. 
Many fibers in anterior part. 
Beginning of lateral ventricles as very shallow broad diverticula from the ventral part of fore-brain 
vesicle. Lateral walls of telencephalon almost 0.5 mm. thick; ependymal layer occupies inner half of 
wall. Recessus neuroporicus a narrow slit, the walls of which are in contact ventrally. A narrow band 
of longitudinally directed fibers lies on either side of the choroid plexus in the upper part of the posterior 
wall of telencephalon. Lateral plexus in cross section twice as high as broad, each containing a single 
blood vessel. Paraphysis appears externally as a distinct fold in dorsal half of diencephalon. Velum 
transversum 0.8 mm. long at median line. Anterior wall three times as thick as posterior. Anterior and 
superior commissures as in preceding stages (No. 28, 29). Pinealis 0.7 mm. in length. Expanded distally; 
no lumen in proximal portion of stalk. Wall of mesencephalon thickened ventrally. Slight differentiation 
of cinerea in ventral zone, into outer and inner layers. Myelencephalon expanded anteriorly, walls lying 
almost in coronal plane. — Short palatine ramus ot glossopharyngeal nerve, and pharyngeal rami of vagus. 
Intestinal ramus of vagus extends posteriorly to stomach. 
Telencephalon extends forward almost to anterior border of mid-brain. 
trally. Cinerea separated laterally into inner and outer layers. Ependymal layer occupies inner third of 
wall. Lateral plexes extend 0.3 mm. into ventricle; free edges expanded but not convoluted. Pinealis 
and velum transversum each approximately I mm. in length at median line. Paraphysis extends forward 
a little over roof of telencephalon. Ventral half of walls of mesencephalon greatly thickened. Deep 
broad median fissure. Cinerea in ventral zone divided into an inner dense, and an outer lighter zone. 
Dorsal longitudinal fasciculi clearly differentiated in posterior part of mesencephalon, lying on either side 
of median groove. Interpeduncular ganglion differentiated in outer zone of cinerea. Beginning of 
formation of valvula of cerebellum. Longitudinal grooves in floor of medulla deeper and more distinct 
than before. Lobus lineae lateralis in most prominent part almost semicircular in cross section. 
Lateral wall 0.5 mm. thick ven- 
Telencephalon much flattened dorso-ventrally; extends forward as far as anterior wall of mesencephalon. 
Lateral walls much thickened (nearly 0.5 mm. in section) ventrally. Ependymal layer occupies approxi- 
mately inner fourth of wall. Cinerea dividing into an inner and outer layer. Recessus neuroporicus a 
deep pit, directed a little dorsally and extending half through the brain wall. Choroid plexus elongated 
and convoluted; expanded distally, secondary folds arising from primary one. Paraphysis expanded 
distally, extending forward on roof of telencephalon. Velum transversum I.o mm. in er at median 
line — its free edge much thickened. Pinealis nearly ı mm. in length, 150 u in diameter distally. Stalk 
small, with lumen occluded at proximal end. Ventral zone of mesencephalon much thickened. Cinerea 
| divided into inner and outer layers. 
Recessus infundibuli a distinct depression, semi- 
elliptical in sagittal section, extending dorsally a 
little on cranial end of hypophysis. Lateral edges 
of anterior part of hypophysis invaginated. 
Walls of recessus infundibuli and recessus mammil- 
laris separated by a deep external groove. Recessus 
infundibuli expanded laterally, the middle three-fifths 
of its cavity connecting with ventricle. Anterior 
part of hypophysis closed off, in the main, from 
mouth, thus forming a shallow sac which extends 
forward nearly to chiasma swelling. Posterior part 
of hypophysis as in preceding stage (No. 27). Distal 
end expanded laterally. 
Hypophysis connected with mouth by narrow stalk, 
250 u. in length (by sections) and 50 u in diameter. 
Stalk contains minute lumen. Dorsal end of hypo- 
physis greatly expanded, and divided into a median 
and two lateral sacculations — the median sac- 
ceulation in contact with recessus infundibuli. 
Transverse diameter of sacculus (recessus) infundi- 
buli 0.8 mm. Median half connected with brain. 
Ridge between recessus mammillaris and sacculus in- 
fundibuli much reduced in height. Hypophysis con- 
nected with oral epithelium by a stalk 60 y. in 
diameter, in which a lumen is barely visible. Slight 
lateral constriction between anterior and posterior 
lobes. Distal end of posterior lobe saccu ated, as 
described for preceding embryo (No. 29). 
Ridge between infundibular and mamillary recesses 
obliterated. Distinct peripheral band of ectoglia in 
tuberculum posterius. Stalk of hypophysis 30 u in 
diameter — lumen obliterated. 
Infundibulum as in preceding stage (No. 31). Marked 
lateral constriction between anterior and posterior 
lobes of hypophysis. Hypophysis stalk a slender, 
twisted column of cells, 0.2 mm. in length, con- 
taining no lumen. 
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