No. 389.] REVIEWS OF RECENT LITERATURE. 429 
quagga, which Lord Morton used in “infecting,” is now an extinct 
species, Ewart uses zebras. He has bred, up to the time of writ- 
ing, nine zebra ¢ horses, ? hybrids, and three reciprocal hybrids. In 
two cases he has crossed a mare with a zebra, and then obtained 
a second foal from the mare mated with a horse. In one case there 
were quite marked stripes; in the second case there were faint 
and few stripes. In two other cases a mare which had already 
had foals by a horse and then by the zebra, had a third foal by a 
horse, and this foal was unmarked. Ewart does not regard the 
stripes seen in the first two cases good evidence for telegony, because 
of the frequency with which such stripes occur on pure-bred foals. 
He finds that foals are far more often marked with stripes — apparent 
or real —than is generally supposed, and that stripes will be often 
seen in horses if they are carefully looked for. Ewart is continuing 
his experiments ; but it seems as though the fact that even marked 
stripes may occur in normally bred foals will interfere with getting a 
satisfactory conclusion concerning telegony in horses. 
Common Salt a Plant Poison. — A solution may have either of 
two injurious effects: it may act osmotically and withdraw from the 
protoplasm the necessary water; it may act chemically. Sodium 
chloride has usually been regarded as acting osmotically only. Now 
True? shows that when a solution of sodium chloride or potassium 
nitrate is made of the same osmotic value as a sugar solution, it is 
far more injurious than the sugar solution, This can only be inter- 
preted to mean that the salt has some additional effect above the 
osmotic effect, and this can only be a chemical one. 
Physics and General Biology.*2— The naturalist has frequent 
need of a good physics. We therefore take pleasure in noticing a 
new text-book on this subject by two professors at Yale University. 
The treatment, while quantitative, does not involve the use of cal- 
culus. Of most use to the naturalist will be the sections on instru- 
ments for measuring time and length; tables of densities of gases at 
various temperatures and pressures and of solids and liquids; surface 
tension, to which an entire chapter is devoted ; solutions (including 
a fairly full treatment of osmosis) ; electric cells and galvanometers ; 
R. H. Physiological Action of Certain Plasmolyzing Agents, Zot. 
Gaze, vol xxvi, pp. 407-416, December, 
2 Hastings, Chas., and Beach, F. K. E. A TextBook of General Physics. 
Boston, ces & Co., 1899. viii + 768 pp., 495 figs. 
