26 BRITISH FRESHWATER RHIZOPODA. 



described by Dr. G. S. West in the ' Journal- of the 

 Linnean Society ' on account of its having the test 

 broad and symmetrical (though the coronal horn is 

 deflected) and its anterior part without constriction. 

 It has peculiarities, however, in the clear chitinous 

 and homogeneous test and the absence of minute 

 diatoms such as Perty represents adhering to it; but 

 there is nothing in these characters which may not be 

 accounted for by environment. In the swamp at 

 Dunham, Cheshire, Ave have met with a form not 

 unlike West's, but with an erect rounded protuberance 





FIG. 45. Difflugia bacillariarum. After Perty, loc. cit. x about 280. 



on the crown instead of a tubular horn a fact 

 which, no less than its general variability, leads us to 

 doubt whether the posterior perforation when present 

 plays any practical part in the economy of the 

 organism. - If it did we might expect it to be an 

 unvarying feature. 



West describes the form which he discovered in 

 Wales as possessing a pale yellow test, through which 

 the protoplasm was distinctly visible ; its body had 

 scattered sand-grains attached, comparatively large, 

 and similar grains agglomerated about the mouth. 

 In the ' Journal of the Linnean Society (Zool.),' 

 vol. xxix, p. 113, the author correlated this form with 

 Difflugia Solowetzldi Meresch., and gave another 

 locality for it in Sutherlandshire. The figure of 



