Normal Plates of the Development of Necturus maculosus. 



17 



Nose 



Hypo- 

 physis 



Mouth 



Digestive System, Liver, 

 Pancreas, Spleen 



Gill, Thyroid, 



Thymus, Trachea, 



Lung 



Urino- 



fenital 

 ystem 



Heart 



and 



Blood 



Vessels 



Skin 



Skeleton 



Limbs 



Stage 



Nasal organ connec- 

 ted with surface 

 ectoderm by short 

 stalk. Clear zone in 

 cells much wider. Or- 

 gan nearly in contact 

 with cerebral hemi- 

 spheres , separated 

 only by a very thin 



layer of mesen- 

 chyma. Fibrous cap- 

 sule denser. Tube 

 much longer; nar- 

 rowed along distal 

 half; stalk extends 



dorso-caudally ; 

 body extends di- 

 rectly caudally. Ven 

 tral portion of wall 



Vi thickness of 

 dorsal. 



First indications of 

 olfactory nerve. 



A solid 

 mass of 

 cells; 

 deta- 

 ched 

 from 

 ecto- 

 derm. 



Mouth 



not yet 



broken 



through. 



Cavity 



well de- 



fined but 



fiUedwith 



yolk- 



bearing 



cells. 



Organ further elon 

 gated caudally. De 

 pressions forming 

 around exterior in^ 

 dicating beginning 

 of lobulation. Cap- 

 sule not so well de- 

 tined as in preceding 

 stage. Organ conne- 

 cted with anterior 

 end of foregut by a 

 solid cord of cells. 

 Pigment beginning 

 to grow around stalk. 

 Olfactory nerve in 

 connection with 

 brain. 



Great- 



elon- 

 gated 

 trans- 

 ver- 

 sely. 



Mouth a 



deep 



trans- 



verse 



groove. 



Cavity 



still mied 



with cells. 



Oesophagus occluded. Liver lies for 

 most part on right side of body. Tu- 

 bules widely separated by sinusoids. 

 Spleen consists of two masses of cells 

 one lying on each .side of mescntery 



Evaginations in wall of stomach indi 

 cate beginning of glands. Gall bladder 

 shows as well defined vesicie with 

 columnar epithelial walls. 



Lumen of stomach sharply marked. 

 Epithelium long columnar cells, still 

 laden with yolk granules. Muscular 

 walls beginning to be formed. Yolk 

 nearly absorbed in posterior end of 

 cloacal walls. Liver further developed ; 

 contains larger number of tubules 

 more compactly arranged. Sinusoids 

 smaller. Gall bladder larger and better 

 defined. Cystic duct and ductus chole^ 

 dochus formed. Dorsal pancreas 

 narrower, its lumen, where it enters 

 gut, constricted to form a duct. An 

 lagen of ventral pancreases appear 

 as dorso-lateral evaginations of ductus 

 choledochus. 



Groove Boundary between stomach and intes- 

 deeper. tine sharply marked owing to greater 



Anlage ofabsorption of yolk in epithelium of 

 teeth. stomach and formation of muscular 



Anlage of wall of stomach. Intestine now much 

 tongue. coiled. Cloaca differentiated from in- 

 testine by greater absorption of yolk. j 

 Oesophagus occluded. Faint saccu- 

 lations indicate beginning of glands in 

 wall of stomach. Hepatic cords wi- 

 dely scattered, separated by large si- 

 nusoids. Cells filled with yolk granules. 

 Gall bladdersmall,lined with columnar 

 epithelium. Empties by cystic duct into 

 ductus choledochus. Dorsal pancreas 

 well differentiated; duct larger except 

 where it enters intestine. Ventral pan- 

 creases contain few tubules. Theirtwo 

 Short ducts j oin cystic duct as it emerges 

 from liver to enter ductus choledochus. 



Gill filaments more 

 prominent. Division of 

 thyroid deepermaking 

 two lines of cells at di- 

 .stal portions. Anterior 

 thymus beginning to 

 be detached from gill 

 arches. Distal portion 

 of tracheal evagination 

 lying closely against 

 ventro-mesial portion 

 of anterior end of sto- 

 mach. Anlagen of right 

 and left lungs in form 

 of tubulär evaginations 

 lying in mesenchyma 

 below lateral margins 

 of Oesophagus. Tulses 



extend caudally to 

 level of posterior por- 

 tion of heart. 



Gill bars much elon- 

 gated. Gill filaments 



better developed. 

 Lungs show now as 

 pair of lateral tubulär 

 diverticula ; epithelium 

 low columnar, nuclei 

 occupying peripheral 

 Position. Anlage of 

 pleura as layer of cu 

 boidal cells. Some 

 mesenchyma between 

 lungs and Oesophagus 



Meso- 



nephric 



tubules 



coiled. 



Open into 



pro- 



nephric 



duct. 



Thyroid divided into 



two portions which are 



Seen in transverse 



sections as small 



groups of cells lying 



just dorso-laterally 

 from the sterno-hj'oid 

 muscle. Lungs slightly 

 longer. 



Gills longer; many 

 filaments. Tltymus, 

 first and second por- 

 tions detached from 

 gill arches, third still 



connected. Lungs 

 longer, further evagi- 

 nated, lumina larger 

 Epithelium low colum- 

 nar, heaviljr laden with 

 yolk granules. Tips 

 reach nearly to level 

 of anterior margin of 

 liver. 



Distal 



ends me- 



sonephric 



tubules 



have 



walls 



thinner 



and in- 



folded. 



Ureters 



very 



small. 



Prone- 

 phros be- 

 ginning 

 to de- 

 generate 

 Meso- 

 nephros 

 extends 

 over 8 

 Segments, 



begin- 

 ning with 

 the 9". 

 Not seg- 

 mental ly 

 arranged. 

 iStubules. 



Pro- 

 nephric 

 tubules 

 still open 

 into coe- 

 lom. An- 

 lage of 

 bladder 

 as slight 

 evagina- 

 tion of 

 ventral 

 wall of 

 cloaca. 



Begin 

 nings of 



trabe- 



culae in 



ven- 



tricle. 



Thick- 



ened 

 to 4 



layers 

 over 

 head. 



Glands 



and 

 Sense 

 cells 

 deve- 

 loped. 

 Few 



Pig- 

 ment 

 cells 

 in 



epi- 

 dermis. 



Cells 

 of co- 



rium 

 slight- 

 ly flat- 

 tened. 



Auricles 



begin 

 ning to 



show 



bilobed 



con- 



dition. 



Walls 

 of ven- 



tricle 



very 



thin ; 



very 



few tra- 



beculae 



Ear- 



liest 



skin 



glands 



in mid 



dorsal 



re- 

 gion. 

 Sense 

 Organs 

 deve- 

 loped. 



Skin 

 glands 



in 

 dorsal 

 regioii 

 well 

 deve- 

 loped. 

 Co- 

 rium 

 cells 

 flat- 

 tened. 

 Base- 

 ment 

 mem- 

 brane 

 for- 

 med. 



Trabeculae extend for- 

 ward to optic nerve; 

 curved downward at 

 anterior end; caudally 

 are continuous with ba 

 sal plate; at level of 

 posterior margin of ear 

 they come together at 

 sides of notochord and 

 grow up on each side of 

 meduUa. Labial carti- 

 lages small, united in me' 

 dian line. Anlage ofse^ 

 cond basibranchial. Ear- 

 liest tracesofossification 

 in base of skull. Layer of 

 Condensed mesenchyma 

 around nasal pits. Otic 

 capsule extending me 

 sially over dorsal and 

 ventral surface of ear. 



Walls of otic capsule 

 chondrified except on 



median and dorsal 

 sides. Neurapophyses 

 appearing in anterior 



portion of trunk re- 

 gion. Pectoral girdle 



chondrified ; narrow 

 scapular portion extend- 

 ing to level of noto- 

 chord ; larger ventral 

 portion (coracoid) ab- 

 out half as long as sca- 

 pular. Humerus chond 

 rified; radius and ulna 

 in procartilage. 



Beginningdifferentiation 

 of hypohyal and cerato 

 hyal, also of first hypo- 

 branchial and cerato- 

 branchial. Second basi 

 branchial developed. 

 Antorbital process for- 

 med. Condensed me- 

 senchyma indicates po- 

 sition of inner nasal 

 plate. Anterior ends of 

 Meckel's cartilage uni 

 ted by procartilage; also 

 lateral margins ofposte 

 rior arches. Occipital 

 processes fused with 

 wall of otic capsule. 



No cartilage in pelvic 

 girdle. Anlage ofneur- 

 apophysis throughout 

 trunk region, none in 

 tail. Neural arches in 

 anterior portion ex- 

 tend dorsallv to top of 

 spinal cord; not united. 

 Caudally neural arches 

 indicated in procarti- 

 lage. Ossification be- 

 ginning around extre- 

 mities of Meckel's 

 cartilage. 



Ante- 

 rior 

 and 

 pos- 

 terior 

 limbs 

 short 

 stumps. 



Ante- 

 rior 

 limbs 

 I mm 

 long; 

 pro- 

 ject 

 dorso- 

 cau- 

 dally. 

 Poste- 

 rior 

 limbs 

 .5 mm 

 long 



Ante- 

 rior 

 limbs 

 pro- 

 ject 

 cau- 

 dally; 



an- 

 läge of 

 digits 

 Poste- 

 rior 

 limb 

 buds 

 point- 

 ing 

 cau- 

 dally. 



Normentafeln zur Entwicklungsgeschichte der Wirbeltiere. XI. 



