FUNCTIONS OF DIFFERENT PARTS OF PROTOPLASM 57 



nucleus and the micronucleus, healed, took in food, grew, repro- 

 duced, and was soon a normal animal. 



Many other similar experiments have been conducted, the results 

 of which indicate that the macronucleus is an essential factor in the 

 metabolism, growth, and regeneration of the organism. The micro- 

 nucleus has to do with reproduction. 



The protoplasm may be divided into cytoplasm and nucleo- 

 plasm. 



Structures found in cytoplasm Structures found in nucleoplasm 



Cell wall (plant cells only) Nuclear membrane 



Plasma membrane Nucleolus 



Vacuole Chromatin granules 



Cell sap Linin network 



Vacuolar membrane Nuclear sap 



Chloroplasts (in some cells) 



Starch grains 



Crystals (protein, urea) 



Centrosome (animal cells chiefly) 



The functions of the different parts of protoplasm. The nucleus 

 consists of very dense protoplasm bounded by a delicate membrane. 

 It may lie am-TN^here in the cytoplasm of the cell. In fact, it is 

 constantly being carried to different parts of the cell by the stream- 

 ing movements of the cytoplasm. It generally contains a minute 

 spherical body, the nucleolus. Sometimes there are several nucleoli 

 in one cell. The exact function of the nucleolus is not known. 



A tj^Dical resting nucleus shows many particles called chromatin 

 granules. These are enmeshed in a network called li?iin. The 

 chromatin granules are believed to be the carriers of hereditary 

 character determiners ; such as, the color of a person's eyes, his 

 disposition, his height, or his artistic ability. These particles are 

 able to absorb certain stains more readilv than the rest of the 

 materials found in the cell. 



The nucleus controls the work of the cell. It is the center of all 

 the physiological activities of the cell; such as, nutrition, respiration, 



WH. FITZ. AD. BIO. 5 



