254 CLAVPOLE. [ VoL. XIV. 
condition suggesting Fig. X, B, is reached (compare Fig. 32 and 
Pl. XXII, Fig. X, B). Later the relations are more like those 
in Fig. XI, C. This suggests a line of possible explanation for 
the conditions found in Anurida. These cells found inside the 
morula, as shown in Fig. 32, ¢c, 6, may originate by a multi- 
_ polar immigration, which is the primitive method of invagina- 
Fic. X, A. Fic. X, B. 
tion. As the second layer of the blastoderm is formed largely 
by the migration of cells that were earlier inside the morula, 
it may be considered to arise by an imperfect and incomplete 
gastrulation. Whether the layer thus formed by migration 
from the inner part of the morula receives any additions from 
the outer layer is uncertain. Cells in various stages of divi- 
sion with the spindle axes directed obliquely to the surface 
point to such a possibility. The origin of the many cells re- 
