The American journal of anatomy The American journal of anatomy . lk cells, which are triangular at the bottom of the appear to be pulling away from the surface as has been notedin other Amphibians. A little later (fig. 29, cf. fig. 23), there are numerous triangularcells about the blastopore whose long axes are all directed dorso-ventrally. In the living egg they are flask- or bottle-shapedwith very long necks. The floor cells of the blastocoele are nowseparating from one another, while the floor itself is the blastopore, it is raised into a tongue, /, leaving a cleft,
The American journal of anatomy The American journal of anatomy . lk cells, which are triangular at the bottom of the appear to be pulling away from the surface as has been notedin other Amphibians. A little later (fig. 29, cf. fig. 23), there are numerous triangularcells about the blastopore whose long axes are all directed dorso-ventrally. In the living egg they are flask- or bottle-shapedwith very long necks. The floor cells of the blastocoele are nowseparating from one another, while the floor itself is the blastopore, it is raised into a tongue, /, leaving a cleft,c, between it and the outer cells as noted by H. V. Wilson andothers. 196 HUBERT DANA GOODALE Fig. 30. The groove has deepened into a sht-Hke archenteron,a, around whose inner ends are the elongated triangular tongue, t, is larger, while the cells of the dorsal lip, d. I.,are smaller and more numerous. The blastopore has lowered toan amount equal to the depth of the archenteron. As I shallshow bv means of artificial stained spots on the egg, the small. 3i Figs. 28-31 cells now lying at the edge of the blastopore are derived by divi-sion from cells which lay at the equator at an earlier stage. Theroof of the blastocoele is thinner, especially above the blasto]) mitotic figures are present just above the floor-cells of the blastocoele are migrating singly or in groupstowards the roof against which they place themselves. This ^ The roof of the egg shown in fig. 30 is unusually thick. DEVELOPMENT OF SPELERPES BILINEATUS 197 migration of yolk-cells, disregarded in recent years, appears,according to Moquin-Tandon (76), to have been first noticed byStrieker in a paper I have not seen. In fig. 31, the blastocoeleis filled with migrating cells, which cause the surface of the livingegg to appear mottled. The archenteron has become enlargedbut there has been little or no more invagination at the dorsal
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