ABSTRACT
Morula-shaped cells, structurally similar to fibre-producing cells occurring in the blood and test of an ascidian, Pyura stolonifera, have been found in the coelomic fluid and Cuvierian tubules of Holothuria leucospilota.
The morula-shaped cells of the holothurian are formed from primitive amoebocytes. They contain globules, each of which consists of a central core of proteinaceous material associated with an unidentified iron compound. A film of polysaccharide materia1, containing granules of a lipo-protein nature, surrounds the core. Part, at least, of the polysaccharide is mucopolysaccharide. It is believed that the materials present in the globules are precursors of collagenous connective tissue fibres.
The mean value of the iron content of the corpuscles was found to be 0·12 g per 100 g dry weight. The iron is organically bound but does not appear to have chemical relationship to haem or other similar iron-porphyrin compounds.
Fibrous processes arise from many morula-shaped cells when they are cytolysed with distilled water.
In hanging-drop preparations some morula-shaped cells eject globules which trail fibres. It is believed that the globules are directly involved in fibre-production.
Granules, similar in many respects to the globules of the morula-shaped cells of the holothurian, have been found in vertebrate fibroblasts.
