MESOGLEA OF HYDRA .I. PHYSICAL AND HISTOCHEMICAL PROPERTIES

The mesoglea of Hydra serves both as a skeleton and as a substratum for cell migration. These functions are made possible in Hydra pseudoligactis by a system of fibers that run along the body column, parallel to the oral‐aboral axis, and perpendicular to the oral‐aboral axis. The fibers are either a mucoprotein or a close spatial arrangement of protein and polysaccharide. They are 0.3 μ in diameter and contain an elastin‐like and collagen‐like protein. Spaced along the fibers are acid mucopolysaccharide‐like particles, 0.7 μ in diameter, which appear to serve a structural or supportive function. Between the fibers are 2.4 μ diameter holes for extension of epithelial cell processes. The remainder of the mesoglea consists of an amorphous gel with a collagen matrix. The physical arrangement of the fibers allows the normal movements of hydra and could also control the direction of cell migration. The arrangement of fibers may be a dynamic system under the control of an enzyme. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company