GENUS AMCEBA— AMCEBA EADIOSA. 61 



stituents of the food ; but I have not seen sand particles or crystals in the 

 e^dosarc, as in other species. 



Large individuals, which I have supposed to belong to Amoeba radiosa, 

 such as those represented in figs. 9-12, pi. IV, approach in character^.- 

 proteus, both in shape and in greater activity, especially when creeping, as 

 seen in fig. 11. Quiescent individuals of large size have at times appeared 

 to me to be undistinguishable from A. verrucosa. 



In creeping on flat surfaces. Amoeba radiosa becomes more or less dif- 

 ferentiated so as to appear to have an anterior and a posterior extremity, 

 from the foi-mer of which radiate a variable number of tapering pseudo- 

 pods. Sometimes these appear to emanate from one or two palmate exten- 

 sions, as seen in figs. 17, 18, which gradually and incessantly change their 

 sliape as the animal slowly glides along. The pseudopods shorten and 

 lengthen, disappear and reappear in the usual manner, and not unfrequently 

 they oscillate from side to side. Sometimes I have observed individuals 

 drag after them adherent particles of sand or other materials, like Amceba 

 proteus and A. villosa, but I have never detected anything like a prehensile 

 process or a villous appendage. See fig. 18. 



There are many organic bodies of very different character which so 

 closely resemble Amoeba radiosa that they might readily be mistaken for it. 

 Such are the colorless blood-corpuscles and primitive ova of animals. 



Dr. Perty* describes and figures bodies resembling Amoeba radiosa 

 which he found in the mucus of the foot of a fresh-water^snail, Lymnceus. 

 He remarks that a small portion contained numerous bodies which he viewed 

 as mucus-corpuscles until he saw them exhibit the usual changes of form 

 of an Amceba. He asks whether these bodies are really young Amcebse, 

 or whether the mucus-corpuscles of sbails have the power of contracting 

 and af putting forth processes. The bodies, judging from the description 

 and accompanying figures, were evidently mucus-corpuscles which exhib- 

 ited the curious phenomenon now so well known as amcsboid movement. 



Thirty years ago I observed similar movements and changes of form 

 in the blood- corpuscles of Helix albolahris and other land-snails, but I was 

 utterly at a loss to account for the phenomenon, and concluded that the 

 movements were due to endosmosis and decomposition. 



In our fresh-water sponges, especially the yellow one which I formerly 



* Keuut. kleinst. Lebensformeu, 1852, p. 188, Taf. viii, Fig. 16. 



