PROTOPLASJM AND CHROMATIN 



93 



from the earliest known stages, in the bacteria and even prob- 

 ably in the ultramicroscopic forms. 



The development of the cell theory after its enunciation in 

 1838 by Schleiden and Schwann followed first the differentia- 



FiG. 12. Protoplasm (gray) axd Chromatin (black) of Amoeba , A Typical Protozoan. 



A group of six specimens of Amceha Umax magnified 1000 diameters; /> = protoplasm; 

 (7;;-. = chromatin substance of nucleus; d = vacuoles. 



I and 5. Two amoebse with the chromatin nucleus {chr.) in the "resting stage." 



2. An amoeba with the chromatin nucleus dividing into two chromatin nuclei. 



3. A parent amceha with chromatin nuclei completely separated. 



4. Protoplasm and chromatin nuclei separated to form two young amoebae. 



After a photograph by Gary N. Calkins. 



tion of protoplasmic structure in the cellular tissues (histology). 

 Since 1880 it has taken a new direction in investigating the 

 chemical and Junctional separation of the chromatin. As proto- 

 plasm is now known to be the expression, so chromatin is now 

 known to be the seat of heredity which Nageli (1884) was the 

 first to discuss as having a physicochemical basis; the ^'idio- 

 plasm" postulated in his theory being realized in the actual 



