298 Notice of Ehrenberg’s Memoir on Microscopic Life. 
left them as mere subjects of ailipement, although at present 
regular professors of electricity and magnetism are established at’ 
all the universities of the civilized world. 
The author hopes that the continuation.of his labors will show, 
that however much that is untenable may have been presented 
in science of late, the objects and results of microscopic research 
are by no means such as to prevent ‘the strictest critical examina- 
tion, and that they can even bagmnceeted to the best of all tests, 
ocular demonstration. 
- He then alludes to his ae with regard to the important 
influence which animalcules have had in filling up streams and 
harbors, and in the formation of deltas, and states that observa- 
tions have now rendered it more obvious how rock-masses which 
are wholly or partially crystalline, may have resulted from the 
solution and change of minute siliceous and calcareous orgall- 
isms. 
Il. Review of the materials.—The author in consequence of the 
various relations of microscopic life to the great field of nature, felt 
induced to compare the facts observed in Europe with the condi- 
tions of other parts of the world, and, accidentally, the American 
forms were the first examined. Among the materials for this 
study of the American forms, were specimens of edible clay 
from the banks of the Amazon, furnished by Von Martius; spe 
cies collected in a living state in Mexico by the author’s brother, 
Carl von Ehrenberg; earth attached to plants in herbaria; and 
“a whole box full” of fossil animalcules sent from the United 
States by Mr. B. Silliman, junior ; by Professors Silliman, Hitch- 
cock and Bailey ; anda number of the living species of West 
Point were received directly from Prof. Bailey in the year 1842. 
From the results of the investigation of these materials, Ehret- 
berg is enabled to present a view of the minutest forms of animal 
life, extending from the Falkland Islands on the south, to Labra- 
dor, Kotzebue’s Sound, Iceland and Spitzbergen on the north. 
Ill. Enumeration of the American forms, according to the 
date of observation.—This detailed enumeration of species from 
different localities is full of interest, but our limits compel us t 
give but brief notices of many of the localities, and to confine 
our attention chiefly to the most important observations concert 
ing the localities in the United States. We remark however that 
among the species detected with sea Confervee from the Falkland 
