REVIEWS OF RECENT LITERATURE. 
GENERAL BIOLOGY. 
Action of Salt Solutions upon Eggs. — Few now underrate the 
value of physiological experimentation as an aid in the advance of 
pure science as well as a basis for practical arts, even though the re- 
sults obtained may be but abnormal states of the organismis studied ; 
it is a hopeful sign of the times that these methods are being so 
actively extended to the study of the lowest organisms and even to 
the sphinx-like mystery of the egg. An important venture in this 
direction is that of Professor T. H. Morgan,' who now adds a second 
paper to his first account of notable discoveries published three 
years ago. 
This paper contains the results of arduous labor, and is illustrated 
by careful drawings. Only a few of the many important facts and 
inferences can be touched upon here. 
The author found that sea-urchin eggs, whether fertilized or not, 
when placed a short time in sea water to which two per cent or less 
of sodium or magnesium chloride has been added, and then returned 
to common sea water, show inside clear spots which change position 
and number. When these eggs are sectioned and stained, the clear 
spots are represented by darkly stained regions and radiating lines — 
in fact “stars” comparable to those seen in karyokinesis. Some 
stars have central specks comparable to centrosomes. 
If the eggs are not fertilized, they may nevertheless, when so 
treated, undergo a process of cleavage into many cells. The cleav- 
age, however, is not like the normal, nor does it lead to the formation 
of larvæ, so far as known. Sections of such eggs show that the 
chromosomes are distributed through the egg, apparently by the 
action of the stars, and that the cleavage of the egg takes place 
about these chromosomes as centers. 
In some other animals, notably a Nemertean and a Gephyrean, 
similar star-formations were produced by treating the unfertilized 
eggs with the same salt solutions. 5 
It is thus possible to bring out stars and centrosomes similar to 
the normal ones, but in abnormal numbers and positions, by mere 
1 Archiv f. Entwicklungsmechanik, 1899, Bd. viii, pp. 448-536, Pls. VI-X. 
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