84 MANUAL OF ELEMENTARY ZOOLOGY 



plasm, and it has been experimentally proved, by opera- 

 tions under the microscope in which the nucleus 

 is removed from the cytoplasm, that nucleoplasm 

 is necessary to the continuance of life. Without it many 

 vital processes, such as fission — which is always preceded by 

 division of the nucleus — assimilation, and secretion, are im- 

 possible, and life soon comes to an end. From these and 

 other facts it appears that the nucleus has a regulative action 

 over the life of the protoplasm. But the nucleus is no more 

 capable of life apart from the cytoplasm than the latter can 



/ St 



W »' e "!■■■■■ 



x>y- 



l.-li. 



..,. /... 



chr. 

 IT- 



Fig. 44. — A diagram of a cell. 



chr., Chromatin granules ; gr., granules in cytoplasm ; #., 

 Hnin meshwork of nucleus ; ««./«., nuclear membrane. 



live without nucleoplasm. Thus the unit of lining matter is 

 a portion of nucleoplasm with its accompanying cytoplasm. 

 Such a unit is known as an energid. A cell is an energid 

 which is in some way separated from the rest of the 

 ■protoplasm of the body. A ccenocyte is a group of 

 energids. 



Protoplasm itself has a fine structure which varies from 

 _ . , tissue to tissue. Under high powers of the 



Protoplasm. . , 



microscope it sometimes appears homogeneous, 

 but usually as a meshwork of varying form composed of a 

 somewhat denser substance known as spongioplasm with a 



