156 
No union was found to exist between the cells of low plants 
where each cell is able to perform all the metabolic functions. An 
exception to this statement must perhaps be made of the Volvox 
and certain others of this family. The fungi were not examined. 
Be. he AG; 
Recent Literature on the Diatomacee. 
Diatomacee of North America. Rev. Francis Wolle. 
There has long been an urgent demand for a work upon dia- 
toms at a reasonable cost. Dr. Wolle has met this want admira- 
bly in the present work. Students of the Diatomacez will also 
appreciate the work which the author has done in bringing 
together a large number of illustrations that have heretofore been 
almost inaccessible, for it is well known that the literature bear- 
ing upon the subject is scattered and costly. A valuable feature 
is the reprinting from “The Lens,” of Prof. H. L. Smith’s 
“Conspectus of the Families and Genera of the Diatomacez.” 
It would have been well, however, if Dr. Wolle had refrained 
from specifying certain genera in the Conspectus, as not North 
American. Several of the genera thus indicated are undoubtedly 
North American. 
The plates, 112 in number, are well executed. It is to be 
regretted that a rather large list of errata in the text has been 
rendered necessary, owing to the author’s serious illness, while 
the work was in course of publication. 
Atlas der Diatomaceen-kunde. A. Schmidt. . 
Fascicles 39 and 40 have just been issued, thus bringing the 
work up to Plate 160. Sendai, Oamaree, and Atlantic City, 
each contribute a number of new species. The continued disa- 
bility of the veteran diatomist, Herr Grunow, has prevented his 
assistance in preparing the present number. | 
On the Structure of the Pleurosigma Valve. T. F. Smith, F. R. 
M. S. 
Diatom Structure—The Interpretation of Microscopical Images. 
Jacob D. Cox, LL.D., F.R.M.S. (Journal of New York 
Microscopical Society, Vol. vii. No. 2. April, 1891). 
Recent improvements in microscopical objectives have ren-_ 
dered possible far more accurate information in regard to the 
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