HISTORY OF ZOOLOGY 

 mf m f 



mk 2 



ik 



mf 



mp 



III. 



FIG. g. Cross-sections through the dorsal region of Triton embryos at different ages 

 (from O. Hertwig). In / the medullary plate (anlage of spinal cord) mp is marked 

 otf from the skin (epidermis, ep) by the medullary folds (mf). In // the medullary 

 plate, by inrolling of the medullary folds, is converted into a groove. In III the groove 

 has closed into a tube (), the spinal cord, which has separated from the rest of the 

 ectoderm (epidermis), c, body cavity (ccelom); ch, notochord; rf>. cavity of primitive 

 somite (myotome); r/z, yolk-cells; ik, entodenn; /<[, lumen of gut; ink 1 , ink-, somatic 

 and splanchnic layers of mesoderm; n, spinal cord. 



