Normal Plates of the Development of Necturus maculosus. 



25 



Nose 



Hypophysis 



Mouth 



Digestive System, Liver, 

 Pancreas, Spleen 



Gills, Thyroid, Thymus, 

 Trachea, Lung 



Urino-genital 

 System 



Heart 



and 

 Blüod 

 Vessels 



Skin 



Skeleton 



Limbs 



Stage 



Compressed 

 anteriorly 



between in- 



fundibulum 



and floor 



of skull; 



broader 



posteriorly. 



Much lobul- 

 ated. 



Liver still larger in 

 caudal portion occupying 



Tip of lung at caudal 

 end of liver. Dorsal walls 



'/j of body cavity. Has of lungs in region ante- 

 several hepatic ducts jrior to liver very much 



entering cystic duct. Gall thinner than ventral wall 



bladder removed some 

 distance from ventral 

 pancreas. Dorsal and 



ventral pancreases have 



united into a continuous 

 mass. 



Lumen of intestine 



larger; epithelium a 



Single layer of poorly 



defined cells. Muscular 



wall very thin, a single 



layer of cells. Few 



hepatic ducts seen in 



body of liver; a few 



enter the cystic duct. 



Dorsal pancreas tubules 



compactly arranged. 



Lungs very much larger, 

 owing to thinness of walls 



very much collapsed. 

 Tips of lungs still show 



embryonic condition 

 Cartilages formed in walls 

 of trachea. Epithelium of 

 lateral walls of trachea 

 much thicker than dorsal 



and ventral walls. 

 Trachea in anterior por 



tion shows columnar 

 cells; ciliated ? At level 

 of heart epithelium flat 



Pronephros compres 

 sed dorso- ventrally; 

 extends over one seg 

 ment. Mesonephros 

 extends over about 10 

 Segments. 



Posterior portion of liver 



divided by transverse 

 fissure into smaller dorsal 

 and larger ventral portion. 

 Gall bladder very laige; 



extends far caudal of 

 liver; lined with flattened 

 epithelium. Cystic duct 

 larger and longer. Pan- 

 creas large extending 

 around dorsal and lateral 



portion of intestine. 



Ducts open into cystic 



duct; show numerous 



branches with tubules 



emptying into them. 



Spleen larger, more 



vascular. 



Intestine forms 6 or 7 

 transverse folds. Intes- 

 tinal cavity very large 

 Muscular wall of midgut 

 consists of two or more 

 layers of cells. In hind- 



gut unicellular glands 

 very numerous. Dorsal 

 and ventral pancreases 

 more intimately united ; 

 dorsal larger and contains 



greater number of tu- 

 bules. Spleen lies just 

 to left of median line in 

 concavity in dorsal wall 

 ot stomach. 



Sexual glands extend 

 far forward ; begin to 

 project down into 

 body cavity; more 

 distinctly separated 

 from mesonephros. 



Trar.heal cartilages 

 better developed at | 

 anterior end. Lungs on 

 either side of stomach. 

 Walls irregularly folded. 

 Left lung still notably 

 shorter than right and 

 lying nearer mesial plane 

 of body. 



Pronephros smaller; 

 lumina of many tubu- 

 les obliterated; duct 

 degenerating. Meso- 

 nephros extends from 

 9" or 10" Segment 

 over about 13 Seg- 

 ments. Müllerian duct 

 not formed yet. 



Unicel- 

 lular 

 glands 

 extremely 

 numer- 

 ous. 



44 



45 



46 



Scapula flattened 



laterally, broad 

 antero - posteriorly. 

 Coracoids meet in 



mid-ventral line. 



Ossification be- 

 ginning in pectoral 

 and pelvic girdles, 

 also in humerus and 

 femur. Sphenoid 

 ossified. Parietals 

 ossified in median 

 portion. Opistho- 



ticum ossifying, 

 also occipital arch. 



Limbs 

 much 



longer. 

 Digits 



longer. 



47 



Normentafeln zur EntwicklungsgehChichte der Wirbeltiere. XI. 



