Facts and Factors of Development 



B 



FIG. i. TYPICAL TISSUE CELLS FROM DIFFERENT ORGANS. A, Epithelial 

 cells from intestine of duck embryo, showing nuclei with dark chromatic 

 masses and clear achromatin surrounded by nuclear membrane, centrosomes 

 as two or three dark granules at the free border of the cells, and cytoplasm 

 filling the cell body. B. Two nerve cells, a. of a ringed worm, b. of a fish, 

 showing cell-body containing nucleus and nucleolus, many neurofibrils and 

 in a one nerve fiber, in b many processes, one of which (-}-) is the nerve 

 fiber. C. Muscle cell from a round worm showing nucleus and cytoplasm 

 in upper part of cell and contractile fibrils in lower part. 



