THE LEUCOCYTES OF ARBACIA PUNCTULATA

Abstract

This investigation revealed the presence of two different types of leucocytes in Arbacia: trephocytes and phagocytes. An outline of their morphology, development and physiology is presented. No genetic relationship between the two kinds could be established, a circumstance which further tends to prove the distinctive nature of each type. Particulate matter derived from the trephocytes and essentially of a nutritive nature, is taken up and incorporated by the growing oöcytes. A considerable fraction of this material has its origin in the red trephocytes which contain echinochrome. It is suggested that the echinochrome found in the eggs of the species investigated may also be derived from the trephocytes. The occurrence of respiratory pigments among invertebrate trephocytes is discussed. It is pointed out that the erythrocytes of invertebrates, as well as the early stages of those of vertebrates, exhibit characteristics of trephocytes. The idea is advanced that the erythrocytes represent a special kind of trephocytes. Formed trephocytic material was seen to be engulfed and digested by the phagocytes of Arbacia. This, as in the case of the oöcytes, is regarded as a normal process of cellular nutrition and lends further support to the thesis, expressed earlier by the writer, that the animal cell takes up and assimilates particulate cellular material in addition to substances in solution. The engulfment and digestion of living trephocytes is described and discussed and additional cases of cellular cannibalism among invertebrates and vertebrates brought forward. The conclusion is reached that cannibalism is a normal and apparently fairly common form of nutrition of the animal cell.