ABSTRACT
The developmental competitions between the two components in the double individuals frequently seem equally balanced, where the two components are of equal size and are equally developed. For very soon after the production of double development from the two blastomeres evidence began to accumulate which questioned the interpretation of the separated cells as an explanation for natural twin formation. The important discovery of the natural process of budding in a higher animal has suggested the probability that twinning in mammals may result in general from a somewhat similar budding process rather than from the early separation of single embryonic cells or blastomeres. The embryonic mass first buds into two growing regions and each of these very soon again divides, thus giving rise to four gastrula-like formations, each of which develops into a complete young armadillo. One of the earliest accomplishments in experimental embryology was the production of two embryos, or twins, from a single egg.
