1 6 MANUAL OF ZOOLOGY SECT. 



ments, it is to be noticed, the Amoeba is influenced to some 

 extent by contact with other minute objects ; when the 

 processes come in contact with small grains of sand or 

 other similar particles, their movements are modified in such 

 a way that the Amceba, in its slow progress onwards, passes 

 on one side of them, so that it might be said to feel its way 

 among the solid particles in a drop of sediment. 



Judging from the nature of the movements, we are 

 obliged to infer that the substance of which this remarkable 

 object is composed must be soft and semi-fluid, yet not 

 miscible with the water, and, therefore, preserving a sharp 

 contour. These and other characteristics to be mentioned 

 subsequently, enable us to conclude that we have to do with 

 the substance of complex chemical composition termed 

 protoplasm^ which constitutes the vital material of all living 

 organisms, whether animals or plants. In Amoeba the 

 protoplasm is clearly distinguishable into two parts, an 

 outer homogeneous, glassy-looking layer completely enclos- 

 ing a more granular internal mass. 



Examination of the Amoeba with a fairly high power of 

 the microscope reveals the presence in its interior of two 

 objects which with a low power we should be likely to over- 

 look. One of these is a small rounded body of a homo- 

 geneous appearance, which preserves its form during all the 

 changes which the Amoeba as a whole undergoes. This is 

 termed the nucleus (Fig. i, nu.) ; it is enclosed in an 

 extremely delicate membrane, and consists of a protoplasmic 

 material differing from that which forms the main bulk of 

 the Amoeba in containing a substance which refracts the 

 light more strongly, and has a stronger affinity for 

 certain colouring matters. The other minute object to be 

 distinguished in the interior appears as a clear rounded 

 space (c. vac.) in the protoplasm. When this is watched it 



