310 CORRESPONDENCE. 
the ploughed field, for organic and inorganic particles, and winnowing 
its dusty harvest over distant and far different areas. These tiny 
Foraminiferal waifs, potent witnesses of the path and doings of the 
wind-storm, being figured by transmitted light only, like those of 1841, 
teach little as to genera and species. 
In these memoirs, and in shorter collateral notices in the ‘ Monats- 
berichte’ of the Berlin Academy of Sciences (namely, for 1838, 1840, 
1844, 1858, &e.), Ehrenberg treated of numerous Diatomacee (“ Poly- 
gastrica”’*), Polycystina,} Foraminifera (“ Polythalamia”), Spongoliths, 
Geoliths, Phytoliths, and other microscopic organisms, which he had 
found, either recent (especially in the Red Sea, the Mediterranean, and 
the North Sea), or fossil in numerous deposits of various ages, such as the 
Mountain-Limestone, Oolite, Chalk, Tertiary, and Post-Tertiary strata. 
Some few of the recent and fossil species referred to in these memoirs 
were figured by him in the ‘ Abhandlungen’ for 1838 and 1839 ; but it 
was not until 1854 that Ehrenberg was enabled to fulfil his earnest and 
laudable desire to give to the world faithful and manifold portraits of 
the well-prepared and almost innumerable microscopic objects on which 
his published opinions had been founded. In 1854 the crowning of 
his favourite labour was accomplished in the publication of the ‘Mikro- 
geologie, with the recognition and aid of the State. In this grand 
work, beside multitudes of fossil Diatomacee, Polycystina, Spongoliths, 
&e., the long-looked-for Foraminifera were depicted, from his own 
drawings, with the best artistic skill, with loving care and right royal 
liberality. There are 4000 figures, in great part coloured, and all, 
except plate 40, magnified at least 300 times linear. 
With regard to the zoological determinations of Foraminifera, 
there is a great discordance between Ehrenberg and other Rhizo- 
podists; nevertheless, taking a broad view of the results of his labori- 
ous, if not accurately discriminative, work among the fossil and recent 
Foraminifera, we may fully acknowledge his having shown that several 
living species are also to be found fossil in Tertiary and Cretaceous 
deposits. Throughout the ‘Mikrogeologie’ there appear numerous 
persistent forms, belonging to the Cretaceous, Tertiary, and Recent 
periods, These his experienced eye readily detected; and in many 
instances his lists show their relationship ; but, for some occult reason, 
he failed generally to characterize them by description and nomencla- 
ture, though often grouped naturally on his plates. As with his 
classification of the Foraminifera among his “ Bryozoa” (1839), so 
with his ‘Mikrogeologie’ (1854), he failed to seize the clue to the 
right understanding and disentanglement of these many-featured 
Rhizopods. Ehrenberg’s truthful plates, however, supply the rhizo- 
podist with a storehouse of beautifully prepared specimens, mostly 
seen by transmitted light; and from these, for by far the most part, 
good and useful conclusions can be drawn, as from fresh specimens, 
except that, being viewed only as transparent objects, with but little 
* The “Polygastrica” of Ehrenberg, or “Infusoria,” comprise Jnfusoria, 
Diatomacee, Desmidiacee, and some Gromide. 
t+ Ebrenberg’s Polyeystina comprehend the Polycystina, Acanthometrina, and 
Thalassicollida of later authors, by whom the whole group is termed Radiolaria. 
