^Sial.OcritTaer'] PROGRESS OF MICROSCOPICAL SCIENCE. 211 
ample suggestions. The author takes up the question whether the 
pollen grains of those families consist of a single cell or of more than 
one. The illustrations are very numerous, and altogether the paper 
shows how much elaborate research may be carried out in so limited 
a subject. — Jahrhuch fiir WissenschaftUche Botanik, 1869. 
TJie Natural History and Development of the Ustilaginece, — This is 
a memoir, copiously illustrated and extending over 100 pages, and 
fully dealing with a very extensive branch of fungology. The author 
is Dr. A. Fischer von Waldheim. We wish the paper could be repro- 
duced in full in our language. 
The Microscopical Structure of the Convolutions of the Brain. — The 
' Journal of Mental Science ' gives the following summary of Mr. Lock- 
hart Clarke's latest researches on this subject. The summary was, we 
believe, prepared by Mr. Clarke for the recent second edition of Dr. 
Maudsley's treatise on the Physiology of the Mind. 
In the human brain most of the convolutions, when properly 
examined, may be seen to consist of at least seven distinct and con- 
centric layers of nervous substance, which are alternately paler and 
darker from the circumference to the centre. The laminated structure 
is most strongly marked at the extremity of the posterior lobe. In 
this situation all the nerve-cells are small, but differ considerably in 
shape, and are much more abundant in some layers than in others. 
In the superficial layer, which is pale, they are round, oval, fusiform, 
and angular, but not numerous. The second and darker layer is 
densely crowded with cells of a similar kind, in company with others 
that are pyriform and pyramidal, and lie with their tapering ends 
either toward the surface or parallel with it, in connection with fibres 
which run in corresponding directions. The broader ends of the 
pyramidal cells give off two, three, four, or more processes, which run 
partly toward the central white axis of the convolution and in part 
horizontally along the plane of the layer, to be continuous, like those 
at the opposite ends of the cells, with nerve-fibres running in different 
directions- 
The third layer is of a much paler colour. It is crossed, however, 
at right angles by narrow and elongated groups of small cells and 
nuclei of the same general appearance as those of the preceding 
layer. These groups are separated from each other by bundles of fibres 
radiating toward the surface from the central white axis of the con- 
volution, and, together with them, form a beautiful fanlike structure. 
The fourth layer also contains elongated groups of small cells and 
nuclei, radiating at right angles to its plane ; but the groups are 
broader, more regular, and, together with the bundles of fibres between 
them, present a more distinctly fanlike arrangement. 
The fifth layer is again paler and somewhat white. It contains, 
however, cells and nuclei which have a general resemblance to those 
of the preceding layers, but they exhibit only a faintly radiating 
arrangement. 
The sixth and most internal layer is reddish grey. It not only 
abounds with cells like those already described, but contains others 
Q 2 
