GENUS DIFFLUGIA— DIFFLUGIA GLOBULOSA. 97 



that, if strictly correct, the shell would be compressed ovoid. Later, he 

 describes the shell as brown, globular, or ovoid and smooth; and the 

 accompanying figure is circular in outline, with pseudopods directed from 

 one pole. 



Ehrenberg, in 1^38, described an oval form, the shell of which is 

 composed of quartz-sand, as Difflugia proteiformis, and attributes this name 

 to Lamarck. To the same he refers one of the three different forms 

 described by Leclerc as characteristic of the genus Difflugia. Lamarck, 

 however, applied the name of D. proteiformis to all the forms indicated by 

 Leclerc, without discrimination. 



Of the three different forms noticed by Leclerc, one is readily recog- 

 nizable as Difflugia spiralis; a second, as D. acuminata; while the third, 

 referred to D. proteiformis by Ehrenberg, from its shape would appear 

 rather to associate itself with the D. piriformis of Dr Perty. 



Dr. Wallich describes a more or less globular form, the shell of which 

 is composed of quartz-sand, or this together with diatoms, as a subspecies 

 of D. proteiformis, with the name of D. globularis. This name he attributes 

 to Dujardin, evidently in mistake for that of D. globulosa. 



Difflugia globulosa, as I have supposed it to be, is not uncommon in the 

 ooze of ponds and ditches, and the smallest examples are frequent among 

 moss, algae, and other plants in damp shaded places. 



The shell varies in shape from oval to ovoid and subpyriform, and to 

 spheroidal and oblate spheroidal, as seen in figs. 25-31, pi. XV, and figs. 

 1-24. pi. XVI. The oral pole of the shell is more or less truncated, 

 and the mouth is large, circular, entire, inferior, and commonly terminal. 

 Mostly it forms the truncation of the oral pole, but sometimes the latter is 

 more or less inflected, and the mouth becomes elevated above the level of 

 the bottom of the shell. Less frequently, the mouth is more or less pro- 

 jected, so as to produce a short neck to the shell. Oval or ovoid varieties 

 of the shell merge into forms which may be regarded as pertaining to 

 Difflugia pyriformis. 



Oblate spheroidal shells, with the oral pole more or less inflected to 

 the mouth, resemble in shape the shell of a sea-urchin, Echinus. 



In structure, the shell, as usual in other species of Difflugia, is com- 

 posed of particles of quartz-sand, as represented in most of the figures 

 above indicated. The smallest specimens frequently consist of chitinoid 



7 RHIZ 



