5 can 
altive 
Normal plates of the development of th 
e rabbit (Lepus cuniculus L.). 
TTS 
Notochord. Axial Skeleton. Skull 
Brain and Cephalic Nerves 
Notochord small, circular in cross section. In region of heart and anterior limb buds, Hemispheres small. Fore-brain, posterior to optic stalks, elongated dorso- 
In heart region, slight | ventrally, narrow laterally; thin ventral plate. Anlage of 3rd nerve, a few 
small notochordal sheath. Loose mesenchyma around brain. 
mesenchymal condensations indicating anlagen of intervertebral ligaments. Notochord, 
medullary tube and post-anal gut fuse in tip of tail. No connection between notochord 
and hypophysis; mesenchyma intervenes. 
Notochord small, circular in cross section, of about the same size throughout. Small | 
hyaline notochordal sheath; around this a slight thickening of mesenchyma. Notochord, 
medullary tube and remnant of post-anal gut fuse in tip of tail. Mesenchyma around 
hemispheres of brain. The mesenchymal condensations, anlagen of intervertebral liga- | 
ments, extend into tail. Notochord ends, somewhat forked, in mesenchyma posterior to 
hypophysis. 
Cephalic end of notochord, just posterior to hypophysis, has a hook-shaped bend. Hyaline 
fibers from ventral region of mid-brain. Motor root of 5th nerve distinct. | 
Maxillary and mandibular divisions of the 5th ganglion; mandibular divi- 
sion in mandibular process. Anlage of abducens nerve from ventral 
region of hind-brain or medulla oblongata. Distinet motor root of facial 
nerve, which runs into hyoid arch. Ganglion petrosum of gth nerve quite 
large; EHRENRITTER’S ganglion small. Ganglion nodosum of Ioth nerve 
larger than jugular ganglion. 1ıoth nerve extends to side of trachea. 
Ganglionic cCommissure of Iıth nerve. Several roots of I2th nerve. 
Varolian bend quite large but curves gradually. 
Mid-brain nearly circular in cross section, large cavity. 3rd nerve distinct' 
Trochlear nerve, 4th, present, emerging from isthmus. Ophthalmic, maxil- 
lary and mandibular divisions of 5th ganglion. In region of 5th ganglion 
hind-brain much expanded; ventral zones level with each other; mantle 
layer quite large. 6th nerve distinct. Motor root of 7th nerve distinct. 
Beginning differentiation of vestibular, cochlear and geniculate ganglia. 
EHRENRITTER’s ganglion and ganglion petrosum of ih nerve; the latter 
large and distinct. Ganglion jJugulare and nodosum of ıoth nerve. IIth 
nerve with small ganglionic commissure. Ventral roots of 12th nerve. 
Hemispheres quite large. Foramen of MoNRo relatively wide. Anlage 
of corpus striatum ? 
Olfactory fibers between anterior end of hemisphere (olfactory lobe?) 
notochordal sheath; around this, a slight mesenchymal thickening. Notochord small, |and wall of nasal cayity. Hemispheres quite large, roughly triangular | 
circular in cross section, of about the same size throughout trunk; a little smaller under 
hind-brain and in tail. Notochord, medullary tube and remnant of post-anal gut fuse in 
tip of tail. Intervertebral ligament anlagen of condensed mesenchyma, extend into tail. 
Anlagen of vertebral centra of mesenchyma, less condensed. Anlagen of neural arches 
and of ı2 ribs of condensed mesenchyma. Anlage of occipital and sphenoidal regions 
of chondrocranium of condensed mesenchyma. MECKEL’s cartilage anlage of condensed 
mesenchyma. 
Notochord ends just posterior to hypophysis with a hook-shaped bend. Hyaline noto- 
chordal sheath. Notochord of about the same size throughout trunk; a little smaller under 
medulla oblongata and in tip of tail. Notochord blends with medullary tube in tip of 
tail. In heart region, anlagen of intervertebral ligaments of dense mesenchyma; vertebral | 
centra precartilaginous; neural arches, precartilaginous, extend dorsad nearly to middle 
of spinal cord; anlagen of ribs, in part precartilaginous, extend ventrad nearly to middle 
of pericardial chamber. Anlagen of basi-occipital and basi-sphenoidal regions of chondro- 
cranium in part precartilaginous. MECKEL’s cartilage anlage precartilaginous. 
Notochord ends with a hook-shaped bend in precartilaginous dorsum sellae. Notochord, 
somewhat irregular, bends to ventral border of precartilaginous basi-occipital region. Here 
cell nuclei of notochord distinct; hyaline sheath; notochord small. Notochord blends with | 
medullary tube in tip of tail. Centrum of cervical vertebra quite cartilaginous; in it, noto- 
chord not visible. Intervertebral ligament of dense mesenchyma; in it, notochord an en- 
larged cell mass, circular in cross section; cells loosely arranged in center. Neural arches, 
becoming cartilaginous, extend dorsad about to middle of spinal cord. Rib anlage, quite 
cartilaginous near vertebra, extends to ventral wall of pericardial chamber; here precarti- 
laginous. Ethmoidal region of chondrocranium of condensed mesenchyma in part precarti- 
laginous. Anlage of membranous skull of thickened mesenchyma. A strip of membrane 
bone near MECKEL’s cartilage. 
Notochord ends in cartilaginous dorsum sellae. Notochord runs along ventral border of, 
basi-occipital region of chondrocranium, where it is very small. Notochord blends with 
medullary tube in tip of tail. In heart region, intervertebral ligament in part precartila- 
ginous; in its center, beginning of nucleus pulposus. Centra of vertebrae cartilaginous: 
in them notochord not visible. Neural arches cartilaginous; extend dorsad beyond middle 
of spinal cord. Ribs cartilaginous near vertebrae. Occipital and sphenoidal regions of 
chondrocranium cartilaginous. Sella turcica indicated in cartilage. Ethmoid region in 
part precartilaginous. Anlage of membranous skull of thickened mesenchyma. MECKEL’s 
cartilage distinct; near it a strip of membrane bone. 
Cephalic end of notochord, irregular, still distinct in cartilage of sphenoidal region caudad 
of pituitary fossa. Notochord blends with medullary tube in tip ot tail, where cells of noto- 
chord are enlarged, vesicular. In cervical region, intervertebral ligament in part cartilagi- 
nous; in it large nucleus pulposus indicated. Centra of vertebrae cartilaginous; in them 
notochord not visible. Neural arches cartilaginous: extend dorsad to dorsal border of spinal 
cord or near it. Ribs cartilaginous: upper ribs join precartilaginous anlage of sternum. 
Ethmoid region in part cartilaginous. JACOBSon’s cartilages present; not much chondrified. 
A little membrane bone of skull, near periotic capsule. A little membrane bone in maxilla. 
Cephalic end of notochord in dorsum sellae still distinct. Remnant of notochord bends along 
ventral border of occipital region of chondrocranium. Notochord blends with medullary 
tube in tip of tail; here notochord cells are enlarged, vesicular. Beginning ossification along 
rib cartilage. Upper ribs join.cartilaginous anlage of sternum. Cartilagınous neural arches 
reach approximately to dörsal border of spinal cord. JACOBSON’s cartilages distinct. Mem- 
brane bone of skull lateral to hemispheres. Considerable membrane bone in maxilla and 
mandible. MECKEL’s cartilage distinct. Mesenchymal thickening dorsal to mid-brain region. 
Cephalic end of notochord distinct in cartilaginous dorsum sellae, irregular in its course. 
Cell structure of notochord still perfectly distinct in this place. Remnant of notochord still 
recognizable along; ventral edge of occipital region of chondrocranium. Notochord blends 
with medullary tube ın tip of tail; here notochord cells somewhat enlarged, vesicular. In 
heart region, intervertebral ligament cartilaginous; distinct nucleus pulposus. No ossifi- 
cation in vertebral centra Cartilaginous neural arches extend dorsad of spinal cord but are 
separated by an interval of some width. Transverse processes well marked. Distinct ossifi- 
cation along rib cartilages, which join cartilaginous sternum. Chondrocranium true carti- 
lage. A suggestion of beginning ossification in median part of occipital region. Consider- 
able membrane bone of skull lateral to hemispheres and a little dorsal to them. Membrane 
bone of skull extends dorso-lateral to mid-brain. Considerable membrane bone in mandible 
about MECKEL’s cartilage, which is distinct. Membrane bone in maxilla. Some membrane 
bone under mesethmoid cartilage; anlage of vomer? 
| (Ganglionic?) connection between EHRENRITTER’s ganglion and ganglion 
| foramen of MOnRO. Choroid plexus of lateral ventricle quite large, vas-| 
[in ventral zones of medulla oblongata; distinct median raphe. Folds of 
in cross section anterior to foramen of MONRO; quite thick mantle layer | 
ventrally and laterally, where wallis thickest. Anlage of corpus striatum? 
Foramen of MONRO relatively smaller than at ı3 days. Fold of choroid| 
plexus of lateral ventricle contains vascular mesoderm. Small beginning | 
of evagination of epiphysis. 3rd and 4th nerves distinct. Anlage of cere- | 
bellum. Vestibular, cochlear and geniculate ganglia differentiated. Anlage 
of choroid plexus of 4th ventricle. Medulla oblongata clearly indicated. | 
} 
| 
jugulare. Varolian bend deep and rounded. 
Distinct olfactory fibers. Corpus striatum extends well anterior in hemi- | 
sphere. Walls of 3rd ventricle thick (thick mantle layer) in region of 
cular. Foramen of MONRO narrow, slit-like. Anlage of pia mater distinct. 
3rd ventricle narrow laterally, long dorso-ventrally. Anlage of epiphysis| 
small Mid-brain thick ventrally across median line, thick Randschleier; | 
small mantle layer ventrally. Thick cerebellar anlage. Thick mantle layer | 
choroid plexus of 4th ventricle. The two limbs of Varolian bend form | 
nearly a right angle. Floor of fore-brain and Varolian bend nearly ap- 
proximated, separated only by a narrow strip of mesenchyma. 
Corpus striatum thick, thick mantle layer. Choroid plexus of lateral | 
ventricle quite large, convoluted. 3rd ventricle narrow laterally. Anlage | 
of epiphysis small; its extremity a little expanded. Cavity of mid-braın | 
large; ventral walls very thick, extending across medıan line, both 
mantle layer and Randschleier thick; anlagen of cerebral peduncles. | 
Thick cerebellar anlage. Anlage of formatio reticularis of medulla. 
Choroid plexus of 4th ventricle. Mid-brain overhangs cerebellar anlage. 
Cortical layer of hemispheres of cerebrum distinct. | 
| 
Anlage of hippocampus major. Choroid plexus of lateral ventricle well | 
developed. Corpus striatum large, joins thick thalamic region ventral 
to foramen of MOnrRO. Very small beginning of choroid plexus of 3rd 
ventricle. A thick bundle of fibers passes from thalamic region into | 
corpus striatum; a condition evident in younger embryos. Epiphysis | 
quite large, much folded. Anlage of posterior commissure? distinct | 
just posterior to epiphysis. Well marked cerebral peduncles. Thick 
cerebellar anlage. Mid-brain overhangs cerebellum. Walls of medulla 
\thick. 
| 
| 
| Hippocampus major quite large. Epiphysis much convoluted. Thick, 
posterior commissure? Mid-brain completely overhangs cerebellar an- 
lage, which is thick. Choroid plexus of 4th ventricle thickly developed. 
Distinct anlage of formatio reticularis of medulla. Cortical layer of| 
cerebral hemispheres well developed. | 
| 
| 
Hippocampus major prominent. Choroid plexus of 3rd ventricle distinct. 
Epiphysis longer than at 17 days; extends a little caudad and dorsad, 
caudal end convoluted, tubular. Thick cerebellar anlage. Varolian| 
bend a right angle. 
Distinct choroid plexus of 3rd ventricle; that of lateral ventricle large. | 
Epiphysis quite large, much convoluted, tubular. Cerebral peduncles 
very thick. Thick cerebellar anlage. Anlage of formatio reticularis | 
in medulla. | 
| 
