312 PROTOPLASM 



outgrowth of the pseudopodium, in contradistinction to the 

 relations that obtain in the drops of foam, since the 

 protoplasm that has come to rest is heaped up and the 

 pseudopodium grows in this way. These relations, as 

 well as those of the simply streaming Amoebae, evidently 

 seem to indicate that it is only at the anterior end of the 

 Amoeba, or at the extremities of the pseudopodia, as the case 

 may be, that sufficient fluidity exists for the extension of the 

 current, and that farther back, on the contrary, in all 

 probability by the action of the surrounding medium, the 

 surface soon becomes more viscid, and the current hence 

 dies down rapidly. That the surface of the body of the 

 Amoeba, and in particular the pellicle, is of a membranous 

 nature, has indeed often been pointed out, and follows with 

 tolerable certainty from other peculiarities. 



In this respect the state of things at the posterior end 

 of many Amoebae must be taken into special consideration. 

 It is notorious that this end frequently bears a tuft -like 

 bundle of fine processes, which have often been compared 

 to pseudopodia. This tuft, however, certainly bears no close 

 relation to real pseudopodia, but is a phenomenon which 

 almost regularly accompanies the retraction of pseudopodia, 

 as can often be very well demonstrated in A. proteus, for 

 instance. In an Amoeba which simply streams along, in 

 which the hinder end is in fact in a continual state of 

 retraction, so to speak, the tuft must naturally attain a 

 special development in this region. If the retraction of a 

 pseudopodium be followed, it may be noticed that it gradually 

 becomes covered with short papillar processes, which 

 pari passu with the diminution of the pseudopodium become 

 narrowed into fine processes, or even become, in part, split 

 up into such, so that finally a tuft of fine processes remains 

 in the place of the pseudopodium. These processes then 

 fuse into a small eminence, which gradually becomes flattened 

 down and passes into the general protoplasmic mass of the 

 body. If numerous pseudopodia are drawn in at the same 

 time, a considerable portion of the surface of the Amoeba 

 may be covered with such tufts. 



The most probable explanation of this phenomenon which, 



