204 Proceedings of the Royal Physical Society. 
by Rosel! in 1755, who gave the name of “der kleine Proteus” to the — 
amceba he had found. Ten years later this amceba was described but not 
figured by Pallas? and renamed by him “ Volvox proteus.” This same 
amoeba was placed by Ehrenberg,’ in 1838, with his Ameba difiuens, a type 
of amceba found by him in Siberia in 1829, and described in 18304 This 
A, diffluens, from Ehrenberg’s description, is clear and limpid in general 
appearance and feeds voraciously on diatoms such as Synedra ulna and 
Navicula gracilis. : 
From the measurements given by this author for A. diffluens, it could not 
have been on account of its size that he considered it to be the same species 
as “der kleine Proteus,” this latter being much larger than his Siberian 
discovery. On account of size and evidently general appearance, Khrenberg 
did, however, separate a large amceba of this type, which he found near 
Berlin in 1831, and gave it a new specific name, Am@ba princeps. 
We may, therefore, presume that “der klewne Proteus,’ and also Volvox 
proteus Pallas, resembled in general appearance the clear, limpid diatom- 
feeding A. diffluens. 
Thus it would seem that Ehrenberg himself divided the amcebe into 
two classes, corresponding with the amcebz here described as A. proteus X 
and A. proteus Y. 
In 1841 Dujardin,” giving no reason but the difference in size of the 
two amcebze, removes Rosel’s amceba, and consequently Volvox proteus, from 
the A. diffluens class and puts it in a class by itself. He gives it an average 
size of 200 », comparable with the A. proteus X of this paper. 
It is obvious that later on the two larger amcebze became confused by 
observers, and generally known under the name of A. princeps, with the 
result that these same observers doubted each other’s descriptions. 
The probability is that Ehrenberg’s Berlin find was the amceba here 
designated as A. proteus Y, but that in his text he describes indifferently 
the diatom and non-diatom feeders under the title of A. princeps when the 
size of the amceba agrees with the limits he has set. | 
Thus Auerbach,® in 1856, objects to Dujardin’s description of A. princeps 
while sure of his own, yet in his illustrations he figures an amceba containing 
ingested diatoms and a nucleus circular in outline. It is only by a 
1 Rosel, Insectenbelust, iii. t. ci., p. 621. 
2 Pallas, loc. cit. 
* Infusionthierchen als vollkommen Organismen, 1838. 
* Ehrenberg, Abh. der Akad., Berlin, 1830. 
° Dujardin, Des Infusoires, 1841, 
6 Auerbach, loc. cit, 
