mesohyl
/ˈmɛsə(ʊ)hʌɪl/Zoology
noun
1In the terminology of J. Hadzi: the primitive or undifferentiated mesoderm of some lower metazoans, especially the mesogloea of cnidarians. rare.
2The gelatinous, largely acellular, inner tissue of sponges lying between the outer layer of cells (the pinacoderm) and the layer of cells lining the internal cavities (the choanoderm).
Origin
1950s. From meso- + ancient Greek ὕλη wood, timber, material.