PHYLUM PROTOZOA 



49 



siderable relative size (c), or mere wave-like elevations of the 

 surface (G). Sometimes specimens are found in which neither 

 nucleus nor vacuole is present ; these are placed in the genus 



FIG 31 -Protamoebaprimitiva. Showing changes of form and three stages in binary fission. 

 (After Haeckel, from Parker's Biology.) 



Protamceba (Fig. 31). Very probably, however, future investigation 

 will show this and other non-nucleate forms to possess a potential 

 nucleus in the form of minute scattered granules of chromatin. 



The largest of the naked or shell-less Lobosa is Pelomyxa, which 

 may be as much as 8 mm. in diameter ; it is multi-nucleate and is 

 further distinguished by the presence of numerous non-contractile 

 vacuoles in the endosarc. 



D 



FIG. 32 A, Quadrula symmetrica; B. Hyalosphenia lata; C, Arcella vulgaris j 



D, Difflugia pyriformis. (From Lang's Comparative Anatomy.) 



Skeleton. We may understand the relation of the shelled to 

 the shell-less Lobosa by supposing an Amoeba to draw in the 

 pseudopods from the greater part of its body, and to secrete, from 

 that part only, a cell-wall ; such a cell- wall or capsule would differ 



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