. Journal of morphology. nuous with the neural folds; through their apposition thedorsal part of the yolk plug becomes closed over. Thus theextreme posterior end of the embryo is undoubtedly formed bya process of concrescence. As shown in later stages, the ventralpart of the blastopore becomes reduced to a transverse slit ( and 178); during this process the yolk plug usually becomesentirely withdrawn into the egg, but a small mass of yolk some-times persists at the surface. The late history of the blastoporeis much the same in Cryptobranchus japonicus, as described byIshikawa (08). EMB
. Journal of morphology. nuous with the neural folds; through their apposition thedorsal part of the yolk plug becomes closed over. Thus theextreme posterior end of the embryo is undoubtedly formed bya process of concrescence. As shown in later stages, the ventralpart of the blastopore becomes reduced to a transverse slit ( and 178); during this process the yolk plug usually becomesentirely withdrawn into the egg, but a small mass of yolk some-times persists at the surface. The late history of the blastoporeis much the same in Cryptobranchus japonicus, as described byIshikawa (08). EMBRYOLOGY OF CRYPTOBRANCHUS 509 At the close of Stage 13 the neural grove has reached a lengthof about 124 degrees; its anterior end usually lies quite accuratelyat the upper vertical pole, while the neural folds extend about16 degrees in front of it. We have seen that the closing blasto-pore marks the approximate position of the vegetal pole; thispole has now rotated a total distance of 56 degrees from the ver-tical
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Keywords: ., bookcentury1900, bookdecade1, booksubjectphysiology, bookyear1912
