190 FEESH- WATER EHIZOPODS OF NOETH AMEEIOA. 



large clear nucleus, which occupies a central position of the fundus. Mostly- 

 several contractile vesicles occupy a position peripherally in the intermedi- 

 ate part of the sarcode mass, just below the position of the nucleus. 



The Filose Protoplasts are usually more sensitive or shy than the 

 Lobose forms, and it is often difficult to induce the animals to project their 

 delicate pseudopods. These are more numerous than in the Lobose Proto- 

 plasts, and are possessed of all the power and capabilities of movement and 

 change of the digitate pseudopods. 



Ordinarily the sarcode of the Filose Protoplasts occupies a greater 

 proportion of the interior of the shell than in the Lobose forms ; and when 

 retracted from the interior surface they remain attached by much fewer 

 threads, and oftener appear separated altogether. 



The shell of the Filose Protoplasts exhibits similar varieties of construc- 

 tion and chemical composition as in the Lobose forms. 



I have learned almost nothing in relation to the modes of repi'oduction 

 of the Filose Protoplasts. I have many times seen pairs of individuals 

 conjoined by the mouth in the so-called condition of conjugation, but ascer- 

 tained nothing of the results. Besides observing certain genera and species 

 in the encysted condition, — that is to say, the sarcode contracted into a ball 

 within the shell and enclosed in one or a pair of additional egg-shaped 

 shells, — I have from time to time seen individuals containing, instead of the 

 ordinary mass of active sarcode, a variable number of globular spore-like 

 bodies, which I have suspected to have resulted from the breaking-up of 

 the sarcode mass. 



PAMPHAGUS. 



Qiee^i, pampJiagos, all-devouring. 



Arcella: Ehrenberg, 1838. Gromia: ScUlumberger, 1845. Cor\j<Ae: Dujardiu, 1852. Pamphagua : Bai- 

 ley, 1853. JDifflugia: Solmeicler, 1854. Corijcia (Dujardiu): Claparfede and LachmanE, 

 1858. Somaiochlamys: Ehrenbcrg, 1871. Plagiophrys ; ZecijtMum : Hcrtwig and Lesser, 1874. 



Animal colorless, transparent, invested with a hyaline, structureless 

 membr9,ne, which is flexible and elastic and concurs strictly with any- 

 changes of form of the body, but. ordinarily restricts such changes, and is 

 not voluntarily extensible. Sarcode always completely occupying the 

 investing membrane, and appearing to be structurally continuous. A large, 

 clear nucleus. Contractile vesicles not distinctly determined. Mouth small, 

 terminal. Pseudopods filamentous, long, exceedingly delicate, branching 

 dichotomously, not anastomosing. 



