GENUS DIFFLUGIA— DIFFLUGIA PYRIFORMIS. 105 



ball occupying the body of the shell. Not unfrequently specimens appear 

 as if the color of the sarcode, as it is ordinarily seen, had undergone a change 

 into a yellowish or brownish hue. 



Difflugia pyriformis was first described with this name by Perty,* from 

 specimens collected in Switzerland. Two of the figures accompanying 

 Leclerc's original description of the characters of the genus Difllugia appear 

 to belong to the same.f These figures EhrenbergJ refers to his own D. 

 proteiformis, attributing the name to Lamarck, § who, however, applied it 

 without discrimination to all the forms, comprising three distinct ones, de- 

 scribed by Leclerc as representing the genus. Ehrenberg's figures and 

 description of D. proteiformis,\\ as I have before intimated, appear rather 

 to apply to the D. globulosa of Dujardin.lt Ehrenberg remarks of D. 

 oblonga, described and figured in the 'Infusionsthierchen' as a form with a 

 purely chitinoid shell, that if it is the same as the D. pyriformis, of Perty, 

 deprived of its incrusting material, as intimated by Claparede and Lach- 

 mann, the latter name should be disused.** This would be just, if we could 

 be positive of the relation of D. oblonga with D. pyriformis ; but in its shape 

 it appears rather to be related with D. acuminata without its point. Carterft 

 and "WallichJJ describe Difflugia pyriformis as occurring both in England 

 and India. The latter author refers the more ordinary form, as a variety, 

 to a subspecies which he names D. mitriformis. Figures of the latter, with 

 one or two points to the fundus, he refers to D. acuminata as another variety 

 of D. mitriformis.§§ 



Lang describes a form under the name of D. triangulata, the figures of 

 which remind me of the knobby variety of D. pyriformis. The shell is 

 described as triangular, flat, membranous, and reticulated.||| 



Difflugia pyriformis by gradual transition merges into D. globulosa, D. 

 acuminata, etc. 



* Kennt. kleinst. Lebensformen, 187. 



tMdm. Mus. Hist. Nat. ii, 1815, pi. 17, figs. 2,3. 



{ Infusionsthierchen, 131. 



§ Animaux saus Vertebres. 



|| Infusionsthierchen, Taf. is, Fig. i. 



ITAn. Sc. Nat. 1837, viii, 311, pi. ix, fig. 1; Hist. Nat. Infusoires, 248, pi. ii, fig. 6. 



**Abh. Ak. Wis. Berlin, 1871,256. 



tt An. Mag. Nat. Hist, xii, 1863, 249. 



XX Ibid, xiii, 1884, 240. 



§$Ibid. pi. xvi, figs. 7, 8, 12 b. 



Illl Quart. Jour. Mic. Sc. v, 1865, 285. 



