58 BRITISH FRESHWATER RHIZOPODA. 



more perfect examples (though they are less common) 

 than 8plia(jnum-\)Og& ; but in the latter are to be found 

 numerous pretty varieties, both spined and spineless. 

 Some spined forms might probably be ranked as perma- 

 nent varieties, but the task of separation would be end- 

 less and unprofitable. There is great force in Penard's 

 observation that it seems more natural to consider the 

 name Difflugia constricta Ehrenb. as applying to a 

 group of forms which it is impossible for the present 

 to differentiate as distinct varieties. One impediment 

 to their study is the infrequency of living examples as 

 compared with the multitudes of empty tests. One 

 filose protoplast, at least Gorythion plati/stomum 



69 



68 



FIG. 68. Oblique view of ordinary form of Difflugia constricta. x 300. 

 FIG. 69. Front view of spined form of the same, x 320. 



sp. nov. simulates D. constricta in the form of 

 its test, and might easily be confounded with it in 

 the absence of the living organism. 



Small spineless forms of D. constricta occur in 

 nearly every tuft of moss found growing in moist 

 places. Where the supply of moisture is intermittent 

 the tests have always a depauperated appearance. 



Genus 19. PONTIGULASIA Rhumbler, 1895. 



Difflugia (pars) CARTER in Ann. Nat, Hist. (3) XIII (1864), 



p. 22. 

 Pontigulasia RHUMBLER in Zeits. wiss. Zool. LXI, 1 (1895), 



p. 105. 



Test similar in construction to that of Difflugia, but 

 differing from it in two marked features, namely, a 



