76 FRESH- WATER RHIZOPODS OF NORTH AMERICA. 



In referring to the mutual convertibility of the endosarc and ectosarc, 

 Dr. Wallich exemplifies the process as it appears to occur in the movements 

 of Amoeba villosa, and the same occurs in a manner exactly similar in Pelo- 

 myxa villosa. He observes that "in the projection of the ectosarc from 

 some area of the general surface, in the form of a hemispherical mass with 

 a broad base, only a very small portion of the original contour line seems 

 to give way at first, so as to admit the passage of the endosarc and other 

 granular contents into the newly projected part, but its entire floor appears 

 to be gradually dissolved, as it were, and free communication between the 

 main body and the new pseudopodal cavity is not established until the com- 

 pletion of this process. Whilst it is progressing the endosarc-granules seem 

 to rush round a corner into the cavity, the corner gradually receding, so to 

 speak, and ultimately becoming altogether obliterated."* 



Sometimes in the projection of a pseudopodal lobe, from the side of the 

 head end of the body, it will continue to be projected, and will gradually 

 receive the endosarc, and with it, as it were, the entire body, when, of 

 course, the animal changes the direction of its movement into that of the 

 pseudopod. This mode of movement is represented in the accompanying 

 woodcut outlines 1-5. 



Pelomyxa villosa ; mode of motion. 



At times, Pelomyxa villosa will appear stationary, or nearly so, and 

 comparatively quiescent, and will project from any part of its surface, 

 slowly or more or less rapidly, a variable number of narrow, conical, or 

 somewhat spindle-shaped, pointed pseudopods of clear ectosarc, as seen in 

 figs. 3, 5, 10. These receive none of the endosarc, and are not used as 

 locomotive organs, but perhaps serve a tactile function. 



I have not observed Pelomyxa villosa assume the branching condition 

 of Amoeba proteus, but under undue pressure I have seen it project one or 

 more long digitate pseudopods, as in the latter. 



The villous area or appendage of the Pelomyxa under consideration 

 resembles that ascribed to Amoeba villosa by Dr. Wallich. In the resting 



•Annals and Magazine of Natural History, 18G3, xi, 370. 



