The American journal of anatomy . a specialized process of gastrulation, thoughEycleshymer notes that the blastopore of Amblystoma does notalways extend symmetrically. It is quite evident from myobservations that the movements of cells are not equally fast on 232 HUBERT DANA jGOODALE h sides of the blastopore. I have described the blastoporeas shifting, but this was merely a convenient view point. Inreality it is due to the shifting of cells relative to the blastopore,, the opening left by infolding cell masses. There is one apparent correlation between this shifting of theblastopore and s
The American journal of anatomy . a specialized process of gastrulation, thoughEycleshymer notes that the blastopore of Amblystoma does notalways extend symmetrically. It is quite evident from myobservations that the movements of cells are not equally fast on 232 HUBERT DANA jGOODALE h sides of the blastopore. I have described the blastoporeas shifting, but this was merely a convenient view point. Inreality it is due to the shifting of cells relative to the blastopore,, the opening left by infolding cell masses. There is one apparent correlation between this shifting of theblastopore and sections. Fig. 36, a cross-section of an egg some-where about this same period of development, shows at the levelof the archenteron floor at the corners a mass of loose cells. Sim-ilar sections through other eggs at this period often show loosecells on one side only of the egg, (fig. 37, right), the cells on theother side, having already become united. The row of cellslining the archenteron at the corners are usually united into a. 74 75 76 77 Figs. 74-77 layer (fig. 36, left side). The separated cells lining the archen-teron at the right (fig. 36) are not found as frequently. Now,the forerunners of the ventral mesoderm and the posterior partof the gastral mesoderm dorsal to the blastopore, lay at the equa-tor of the egg before gastrulation began. It is not unreasonableto suppose that the mesoderm cells which are to lie in the vacantplaces shown in fig. 36, also lay about the equator of the only other assumption necessary is to suppose that thesecells are not invaginated at exactly the same time the rest of thecells are, but that they move somewhat independently of thegeneral process. It is easy to derive a large part of the mesodermcells from the floor cells of the blastocoele, since they can be seenactively migrating into i)ositions where they must eventuallybecome mesoderm. The yolk-cells of the equatorial region arenaturally somewhat less free to pursue an entirely i
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectanatomy, bookyear1901
