TISSUE FORMATION. 67 



Some of the latter have cilia, or hair-like projections, 

 whose motions produce a current over the surface. 



A 



FIG. 21. Connective-tissue. A. White and yellow fibers. B. Developing Cells of 

 connective tissue. 



Thus the skin, or mucous membrane, is not a continu- 

 ous membrane, but made up of cells, the nuclei of which 

 exhibit the remains of the bioplasm or living matter 

 from which they sprang. (Fig. 22.) 



FIG. 22. Epithelial cells, i. Squamous epithelium from the skin, showing the change 

 from bioplasm to horny scurf. 2. Tessellated Ep. from serous membrane. 3. Columnar 

 Ep. from intestine. 4. Ciliated Ep. from air-passages. 



