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. 3] .— Protamoeba primitiva. Showing changes of form and three stages in binary fission. 

 (After Haeckel, from Parker's Biology.) 



Protamoiba (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 Pdmnyxa, 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. 



Fig. 32.— a, Quadrula symmetrica j B. Hyalosphenialata; C, AreeUa vulgaris ; 



D, Difflugia pyriformis. (From Lang's Comparative Aiiato,n/j.) 



Skeleton. — We may understand the relation of the shelled to 

 the shell-less Lobosa by supposing an Amceba 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 



VOL. I 



