62 FRESH-WATER RHIZOPODS OF NORTH AMERICA. 



described under the name of Spongilla fragilis* I have repeatedly observed 

 amoeboid corpuscles which I supposed to be parasitic, but which are now 

 regarded to be ova of the Spongilla. These corpuscles bear so close a 

 resemblance to Amoeba radiosa that it is not improbable isolated ova of 

 Spongilla have at times been mistaken for it. 



The Spongilla amoeboids, as represented in figs. 19, 20, pi. IV, from 

 specimens taken from the scrapings of a Spongilla fragilis obtained from 

 the Schuylkill River, in July, ordinarily resemble Amoeba radiosa in the 

 swimming condition. They have a stellate appearance with a spheroidal 

 body and a variable number of pseudopods radiating in all directions. 

 They remain suspended, almost motionless, in the water, but feebly vaiy the 

 shape of the body, and slowly project or withdraw a pseudopod, or change 

 its form or direction. The body consists of a mass of pale granular pro- 

 toplasm with variable proportions of yellowish grannlar balls looking like 

 food. It contains a nucleus, which is often obscured by surrounding mate- 

 rials. It has also a contractile vesicle, which exhibits the characteristic 

 movements, though comparatively with exceeding slowness. Not unfre- 

 quently several contractile vesicles occur. The pseudopods are long, 

 tapering, and pointed, and are composed of ectosarc with only the finer 

 protoplasm of the endosarc. Associated with the amoeboids resembling 

 Amujba radiosa, are others, as represented in fig. 21, which in their appear- 

 ance and slow movements resemble A. verrucosa, though they are no doubt 

 of the same character as the former. 



AMCEBA VILLOSA. 



Plate I, figs. 9, 10; II, figs. 14-16; VIII, figs. 1-1G. 



Amoeba. Wallich: An. Mag. Nat. Hist. 1863, xi, 287, pi. viii. 



Amoiba vMoea. Wallich: Ibidem, 363, pi. ix, 434, pi. x, figs. 5-9. — Duncan: Pop. Sc. Rev. 1877,217, 



pi. vi, figs. 38-40. 

 Amoeba princeps. Carter: An. Mag. Nat. Hist. 1863, xii, 30, 44, pi. iii, figs. 1-3. 

 Trichamoiba kirta. Fromontel: Etudes Microzoaires (no dale), 345, pi. xxviii, fig. 4. 



Animal in motion differentiated into an anterior and a posterior region, 

 ordinarily more or less sausage-shape or irregularly clavate, or palmate in 

 shape, and commonly with few lobate, or short thick digitate, or conical 

 pseudopods, consisting of extensions of the sarcode preceded by more or 

 less thick portions of clear ectosarc, and mostly directed foi'ward; posterior 

 extremity commonly somewhat narrower, and terminating in a villous area 



*Proc. Acad. Nat. Sc. 1851, 278; 1874, 145. 



