REVIEWS. 
On an Undescribed Form of Ameba. 
Unprr the above title, Dr. G. C. Wallich has lately pub- 
lished some very interesting observations on “ Amcebe, and 
allied forms of Rhizopoda,” in the ‘ Annals of Natural His- 
tory.’* In certain ponds on Hampstead Heath he obtained 
a curious form of Ameba in considerable quantities, and is of 
opinion that the peculiar characters presented by them are 
normal, although, perhaps, not permanent in their nature. 
“According to the descriptions of the commoner forms, such 
as A. princeps, A. diffiuens, or A. radiosa (which he believes 
ultimately will be found to be mere transitory phases of one 
species), it appears that the sarcode-substance is uniformly 
differentiated into ‘endosarc’ and ‘ ectosare’—ain fact, 
neither the outer layer of sarcode nor the more viscid 
mass within is endowed with a more advanced degree of de- 
velopment at one point than at another.” In the variety 
which Dr. Wallich describes this is not the case, one portion 
of the ectosare in it exhibiting a structure differing per- 
manently from the remainder, being densely studded with 
minute papille, “which,” says Dr. Wallich, “in the quies- 
cent state of the creature, are of nearly uniform aspect and 
size, and cause the surface upon which they occur to resem- 
ble the villous structure of mucous membrane in outward 
appearance. When the animal moves, these papille or villi 
vary in length, and now and then several coalesce, so as to form 
processes more nearly approaching the ordinary pseudopodial 
character, although still of minute proportions. The villous 
patch, which occupies probably from -!,th to ~\,th of the entire 
superficies, appears frequently to be employed as a prehensile 
organ, the creature being enabled through its agency to 
secure for itself a continuous point d’appui, from which the 
rest of the body is pushed or flows onwards.” True pseudo- 
podia are not projected from this villous patch, but are freely 
thrown out from the remaining portion of ectosare when 
* Annals and Magazine of Natural History’ for April, May, and June, 
1863. 
