30 HISTOLOGY. 
CHAPTER IV. 
HISTOLOGY. 
ISTOLOGY is the study of cells. In the case of 
the Protozoa this is the study of the whole organ- 
ism; in the AMe¢azoa, of its constituent units. 
Fig. 4.—AMGBOID CELLS. 
I 2 3 
1. Ameeba. z. Leucocyte of Frog. 3. Ovum of Hydra. 
(After Howes.) = (After KLEINENBURG.) 
Independent cells may occur in several character- 
istic conditions. The principal are as follows :— 
1. AMa@Boip.—These are cells resembling Amba, shape- 
less, and showing movements by pseudopodia. A number 
of Protozoa show this condition throughout the greater part 
of their life. In the MZetazoa free amceboid cells occur with 
great frequency They are usually termed /ewcocytes and 
fulfil important functions, such as ingestion of bacteria. 
Leucocytes of this nature occur in great numbers in human 
blood. 
Fig. 5.—FLAGELLATE CELLS. 
ran 
1. Spermatozoa. 2 Flagellate Protozoa. 3. Collared Cell of 
Sponge. 
