154 NOTICES UF BOOKS. 
important generalisation that free-cell formation has itself been derived 
from cell-division by curtailment of the various processes contingent 
on the latter. Where the free-formed new cells preserve the position 
they would occupy if produced by division, a less differentiated type is 
presented than where they occupy no stated position with respect to 
each other. The most profound modification is, he thinks, met wit 
in the angiospermous embryo: sac, where free formation (of the embryo- 
preservative fluid, it will probably make an epoch in microscopic 
In the zoospores of Vaucheria sessilis examined by aid of osmic 
acid, the granular protoplasm is found to be bounded externally by an 
egranulate layer (Hautschicht), with transverse rod-like markings, of 
which latter the cilia are continuations (fig 12). The plasmodium of 
thalium in the act of contraction shows a number of cilia-like pro- 
longations of the ‘‘ Hautschicht ” (fig. 13). Prof. Sesastinngeethinks that 
the ‘‘ Hautschicht,” which may or may not be te (in the latter case 
la: al h un 
(eg., those of Spiregyre) with ae extension a 
movement: win’s recent discovery of pro Geactnatie exten- 
sion from cells Suit appear to confirm the. soundness of this com 
ison.* 
For the purposes of this notice we have used the French translation, 
which had the advantage of the author’s supervision eg notice that 
eta edition of the German work has appe eared ; have not 
yet seen, but should it prove erent from its iciencaont on any ~ 
Lidentiat int we s inform our readers. 
_ We have reproduced in the accompanying plate some of Dr. Stras- 
burger’s illustrative -— 
EXPLANATION OF Tas. 188. 
Fig. 1.—Ripe ‘‘egg” or central cell of the a (corpusculum) of 
Ephedra altissima, containing frothy protoplasm at its ‘‘ upper” part, granu 
inits ** =. three-fourths, the nucleus near the boundary between 
the ular and frothy protoplasm, and the canal-cell, resulting from division 
of tho nucleus, atthe apex (structural base). x1 Lbs 
Fig. 2.— Pollen-tube applied to the disarranged cells forming 
the mouth . —_— the archegoniam, Nucleus not yet dissolved. x 100. 
Fig. 2 further stage, showing the nucleus dissolved, and 
ek senate ica Ae in the longitudinal axis. x 100. 
3.—The same. Free-formed cells, the nuclei of which first appear it in 
* Abstract in Quart. J ourn. of Micros, Sc.. ee oe oe th ede scl omnees 
Mr. Vines gives : an account, in some detail, of 
