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Quarterly Journal of Microscopical Science, Vol s3-105, 7-11, Copyright © 1964 by Company of Biologists

The Fine Structure of the Respiratory Tree in Cucumaria

WILLIAM L. DOYLE 1 and G. FRANCES McNIELL 1

1 Department of Anatomy, University of Chicago

The delicate tubules of the respiratory tree consist of 4 layers: a lining epithelium, a thick mucoid layer containing collagenous filaments, a smooth muscle net, and a coelomic epithelium. The free surfaces of both epithelia have well developed plasmodesms. Amoebocytes are present in all layers and the spherules of one type are considered to be precursors of the mucoid substance; another amoebocyte may be a fibroblast. Perpendicularly oriented smooth muscle fibres, as well as those parallel to each other, are linked by desmosomes ensuring synchronous contraction. Secretory activity is evident in distended cisternae of the endoplasmic reticulum of certain epithelial cells and in the vacuoles of the lining epithelium.






© The Company of Biologists Ltd 1964