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Notices of Books. 
nuclei, and cytoplasm, are explained on this theory by the author 
as follows. Treatment with water causes in many cases well-marked 
vacuolation of the chloroplastids ; this is due to the swelling-up of 
the fibrillae, the chloroplastin, and to the solution of the metaxin. 
In some cases vacuolation does not take place because, apparently, 
the chloroplastin does not swell sufficiently to cause the separation 
of the fibrillae. That a proteid substance is actually present in solution 
in the vacuoles at the chloroplastids can be shown by reagents 
inducing precipitation, etc. 
Treatment with -water also frequently induces vacuolation of the 
nucleus : this appears to be due to the swelling of the nucleus as a 
whole, and to the solution of the paralinin. 
The vacuolation of the cytoplasm is peculiar in that it does not 
appear to be due to the presence of a soluble proteid, as is the case 
in the chloroplastid and the nucleus — at least Schwarz failed to 
detect any such substance ; — but no suggestion is made as to what 
the soluble substance may be. Vacuolation does not, however, take 
place in very young cells, in which the cytoplasm simply swells 
by imbibition ; neither does it take place in old cells in which the 
cytoplasm is scanty, nor in cells which contain tannin ; in these 
latter cases there is also no swelling by imbibition. 
In conclusion, the chemical properties of these various substances 
are considered. 
Chloroplastin and cytoplastin appear to be closely allied. The author 
rejects the suggestion of Zacharias that the plastins are identical with 
the insoluble nucleins, though they resemble them in some respects, 
on the ground that whereas these nucleins are soluble in strong 
potash and in concentrated hydrochloric acid, neither chloroplastin 
nor cytoplastin dissolve in these reagents, nor do they stain readily, 
as do the nucleins. 
The differences between chloroplastin and cytoplastin are slight. 
Cytoplastin dissolves slowly in 5% disodium phosphate, and swells 
or even dissolves in 20% solution of the salt, whereas chloroplastin 
swells but little and does not dissolve in these solutions. 
Metaxin appears to be an altogether peculiar proteid. Although 
the metaxin of the chloroplastid dissolves on treating a chloroplastid 
with water, yet the author doubts if it is actually soluble in water, 
for the observed solution may be due to the alkalies which, as has been 
shown, are present in the protoplasm. However, since it is stated, in 
