THE CELL. 



endlessly diversified. Cells may assume almost any conceivable 

 form, and there are even cells (e.g., Amccla, or the colorless cor- 

 puscles of the blood) which continually change their form from 

 moment to moment, passing through grotesque transformations 

 which would be incredible did we not actually behold them. 

 The variations in structure may involve any or all of the three 

 characteristic parts of the typical cell, being at the same time 

 accompanied by variations of form. It is easy to understand 



therefore, how cells may vary end- 

 lessly in appearance, while conform- 

 ing more or less closely to the same 

 9 f & i general type. 



Variations in Form. Free cells 

 are, as a rule, bounded by curved 

 surfaces (as in the star-fish's ovum), 

 while those which are united in 

 tissues, especially when crowded, are 



FIG. 22. Series of cells showing grada- 

 tions between spherical and elongated 

 forms. (From various sources and dif- 

 ferently magnified.) 



FIG. 2.3. (After Klein.) Flattened cells 

 arranged in a layer <" pavement epi- 

 thelium"), from the surface of the 

 diaphragm of a rabbit. 



usually bounded by plane surfaces and possess angular contours, 

 owing to mutual "pressure. If yielding spherical bodies (or cells) 

 be crowded together they tend to assume regular twelve-sided 

 forms (dodecahedrons), as may be seen in the experiment with 

 soap-bubbles already referred to. 



Now in comparing the forms of cells we may trace every 

 gradation from the typical spherical ceil, taken as a starting-point, 

 (or its polyhedral representative among angular cells) through 

 oval, oblong, cylindrical, or prismatic forms, to those which are 



