The Fine Structure of Intercellular 

 and Mesogleal Attachments 

 of Epithelial Cells in Hydra 



Richard L. Wood 



Department of Anatotny, University of WasJiington Scliool of Mediciiie, Seattle. 



Cellular interactions in multicellular organisms have been ex- 

 amined both from the physiological and the morphological 

 points of view. As a result of these studies it has become clear that 

 there are certain general features of epithelia which are related to 

 special kinds of adhesive properties. It is further realized that 

 these special adhesive properties are not distributed uniformly over 

 the cell surface. The epithelial layers of hydra share these general 

 properties of epithelia, although the details of intercellular attach- 

 ment sites seem not to have been studied extensively in the past. 



Hydra consists essentially of a bicellular leaflet of epithelia and, 

 therefore, is well suited for studies of epithelial cell interactions. The 

 epithelia of hydra are perfectly good epithelia, but at the same 

 time the individual cells serve several functions, many of which are 

 not usually associated with functions of epithelium in a single layer 

 in higher organisms. The presence of well developed terminal bar 

 type attachment areas between these epithelial cells of hydra is 

 certainly to be expected from our knowledge of higher organisms. 

 Such areas do occur and the detailed structure differs from previ- 

 ously described intercellular attachments. 



Basal processes of many epithelial cells in hydra contain muscle 

 fibers. Special relationships between adjacent muscle fibers and 



^This research was aided in part by Grant No. H-2698 from the National Institutes 

 of Health, Public Health Service. 



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