28 



THE CELL 



Very similar in appearance to the Amoeba, bat much smaller in 

 size, are the white blood corpuscles and the lymph corpuscles of the 

 vertebrates (Fig. 8). If they are examined just after they have 

 been taken from the body of the living animal, they are seen to 

 be more or less globular masses of protoplasm, each one consisting 

 of a scarcely visible hyaline layer, enclosing a granular internal 

 portion in which the nucleus is situated. However, whilst the 

 specimen is fresh, this nucleus can hardly be distinguished, and 

 sometimes even is quite invisible. After a time, the little body 

 begins to push out from its surface, processes similar to the pseudo- 

 podia of the Amoeba. 



7. FIG. 8. 



FIG. 7. Amoeba protews (after Lei^y : from R. Hertwig, Fig. 16) : n nucleus ; cv con- 

 tractile vacuole ; n food vacuoles ; en endoplasm ; ek ectoplasm. 



FIG. 8. A leucocyte of the Frog, containing a Bacterium which is undergoing the 

 process of digestion ; the Bacterium has been stained with vesuvine. The two figures re- 

 present two successive changes of shape in the same cell. (A.fter Metschnikoff, Fig. 54.) 



Myxomycetes and Reticularia, which also consist of naked proto- 

 plasm, are very different in appearance. The Myxomycete, which 

 is best known to us, is the JEthalium septicum, which forms the 

 so-called powers of tan and grows over large portions of the surface 

 of tan-pits, during its vegetative condition, like a thin coherent 

 skin of protoplasm (plasmodium). 



Chondrioderma is another slime fungus which is nearly allied to 

 the above. A small piece of its edge is represented in Fig. 9. 



