GENUS ACTLNOSPH^ERIUM— ACTIXOSPH^EKIUM EICHHOENII. 259 



or less distinctly defined from the interior mass by greater size, translu- 

 cency, and apparently the intervention of a thicker film of granular pro- 

 toplasm. Nuclei numerous and imbedded in the latter beneath the periph- 

 eral vacuoles. Contractile vesicles two, commonly occupying opposite 

 positions in the peripheral vacuole layer. Rays numerous, consisting of 

 tapering extensions of the granular protoplasm, including an axis thread, 

 which starts from the body beneath the peripheral vacuole layer. 



ACTINOSPttERIUM EICHHORNII. 



Plate XLI. 



Der Stern. Eichhorn : Beitr. Kennt. Wasserth. 1783, 15. 



Actinophrys Eichhoraii. Ehrenberg : Bencht Preus. Ak. Wis. 1840, 198. — Stein : Infusionsthiere, 1854, 148, 

 151. — Claparede and Laehmann : Etudes Iufusoires, i, 1858, 9, 450. — Pritchard : Hist. Infu- 

 soria, 1861, 560.— Haeckel : Radiolarien, 1862, 165.«-Wallich : An. Slag. Nat. Hist, si, 1863, 

 444, pi. x, figs. 1-3.— Carter: Ibidem, 1864, xiii, 35, pi. ii, fig. 21; 1865, xv, 281, 283, pi. xii, 

 fig. 6.— Cienkowski : Arch. mik. Anat. i, 1865, 227, 229.— Greeff: Arcb. mik. Anat. iii, 1867, 

 396. — Micro-graphic Dictionary, pi. 23, fig. 7 a. — Schneider: Zeitsch. wis. Zool. xxi, 1871,507. 



Actinophrys sol. Kolliker : Zeitsch. wis. Zool. i, 1849, 198. 



Actinospktxrium Eiehlwrnii. Stein: Sitzungsb. Bohm. Gesells. Wis. 1857, 41.— Greeff: Sitzungsb. nieder- 

 rhein. Gesells. Bonn, 1871, 4.— Schulze: Arch mik. Anat. x, 1874, 328, Taf. xxii. — Hert- 

 wig and Lesser : Arch. mik. Anat. x, 1874, Suppl. 176, Taf. v, Fig. 1. — Leidy : Pr. Ac. Nat. Sc. 

 1874, 166. 



Body transparent, colorless, usually with a single peripheral layer of 

 the large vacuoles, which are deeper than broad ; or, in the larger or older 

 individuals, sometimes with two peripheral layers of vacuoles of more uni- 

 form diameters. 



Size — Ranging from 0.088 mm. to 0.4 mm. in individuals of globular 

 form, with rays to 0.22 mm. in length ; in individuals of oval form, from 

 0.26 mm. by 0.24 mm. to 0.G8 mm. by 0.65 mm., with rays as in the former. 



Locality — In ponds, lakes, and ditches, among Ceratophyllum, Lemna, 

 and other aquatic plants, in Pennsylvania, New Jersey, and the Uinta 

 Mountains of Wyoming Territory. 



Actiiiosphaerium eichhornii conmionly looks like a giant form of 

 the common Sun-animalcule, but is usually readily distinguishable, even 

 in the smallest individuals, by a more or less well-marked distinction 

 of the peripheral layer of vesicles from the interior mass. It varies greatly 

 in size, and, though less frequent than Actinophrys sol, is found in similar 

 positions, and possesses nearly similar habits. See pi. XLI. 



The body is mostly spherical, but often in the largest individuals is 

 oval. It forms a colorless, hyaline, vesicular ball, with a clouded interior 



