Preliminary remarks, Symmetry of hydroids, General notes, Colony formation in sponges, Colonies of siphonophara, General remarks, Trilubites, Kamptozoa, Bryozoa
Sturctural and organological differentiation of the lower metazoa,Modifications and products of kinetoblast,Neural appoaratus,Protective adaptations of kinetoblast,Primary body Layers of the lower metazoa