Studies on the amphibian digestive system. III. The origin and development of pancreatic islands in certain species of anura

A study is made of the pancreatic islands in Rana clamitans, R. catesbiana, R. sylvatica and Hyla versicolor during various stages of development. The islands, which were first seen in the 8‐mm. R. clamitans larvae, originate from the endodermal cells of the primitive pancreatic anlagen. Following early larval development in all of the species, new islands differentiate from the cells of the pancreatic ductules. During metamorphosis, much of the acinous tissue degenerates, but the islands persist. They become aggregated and the definitive islands are formed from the primary islands before the mature adult stage is reached. With the azure‐eosin technique, two types of island cells were distinguishable before, or at the time of metamorphosis, in all of the anurans studied. They are designated as the red and blue types. The blue cells are considered the primitive or embryonic type, and may transform into the red type; or the red type may originate independently.