Plate XIX. 



Vil., collectino; dnet. 



cil., chorda dorsal is. 



f'.j)., coelomic projection. 



cul ., cutis-layer of myotome. 



(1., dorsal row of mesoLlast. 



ep., epiblast. 



((J., fore-giit. 



/., Anlage of liver. 



hy., hypoblast. 



Lm., lateral plate of mesoblast. 

 ■hl., median row of mesoblast. 

 mcli., mesenchymatous cells. 

 'iiif^., mesoblast. 

 m.p., parietal layer of mesoblast. 



nii.I, IT, AT., the first, second, cIt. 



myotome. 

 onus., muscle-layer of myotome. 

 m.v., visceral layer of mesoblast. 

 n., neural canal. 

 nst.2-3, nephrosti^me the second 



and third. 

 pp.1-3, peritoneal partition. 

 pp.c., pleuroperitoneal cavity. 

 pt.1-6, pronephric tubules from the 



first to sixth. 

 seit., subchorda. 

 S(l., segmental duct. 

 sg., spinal ganglion. 

 V. ventral row of mesoblast. 



Figs. 60-63. From the same series as, and the posterior continuation of, 



fig. .59. 

 Figs. 64-76. From a series of transverse sections through an oldest embryo 



of Stage III. 

 Figs, 77-81. From a series of transverse sections through an embryo of 



Stage IV ; hence the body of embryo in the |)resent stage is twisted, 



the sections pass through unavoidably ol)lique planes. 



