290 The American Naturalist. [March, 
Watase regarding the pre-formation and early localization of embryonic . 
- organs. While Roux held that the frog’s egg is a mosaic in which 
definite regions must become certain organs, the following experi- 
ment of O. Hertwig seems to show that this is unlikely in the related 
form, the Triton. 
When the egg of Triton palmatus and T. cristatus taken in May and 
June 1892 was dividing into two cells, a delicate silk thread was 
passed around it and drawn together so as to gently squeeze the two 
first cells somewhat apart. This made the egg somewhat dumb-bell 
shaped. 
Each cell divided and finally an embryo with chorda, somites and 
nerve tube was formed. As the embryo was not formed so as to lie 
with its left on one of the hemispheroid parts of the egg and its right 
upon the other, we may conclude that the first cleavage did not divide 
the Triton egg so as to separate its right-forming from its left-forming 
material. The right and left halves are not separated by the first 
cleavage. In fact in one case the thread separated the head from the 
tail region. 
It is only, the author thinks, by understanding the multiplication of 
the egg as an organism and the gradual interaction of the numerous 
cells of any stage that we can arrive at a true conception of the 
epigenesis-like formation of an embryo. 
Form and Chemical Composition.—Curt Hebst* of Zurich 
has published a series of experiments made at Naples and at Triest in 
the endeavor to determine if the form of organic structures is dependent 
upon their chemical composition. To this end the eggs of sea urchins, 
(three species were tried), were reared in sea water to which definite, 
small amounts of certain salts were added. The salts used were LI 
Cl, Li Br, Lil, Li NO,, Li, SO, Na Br, NaI, Na, SO, Na NO, K 
Cl, KBr, KI, K NO,, K,, SO, RhCl, CsCl, Mg SO, and Ca Cl, ; the 
results obtained were certain peculiar forms of larvæ, and the expla- 
nation adopted for the results was that the salts acted osmotically, not 
iby altering the chemical constitution of the eggs. 
Before speaking of the character of the larve reared under these 
abnormal conditions we will first note a few incidental results sometimes 
seen. One is that in a number of eggs, two blastule were seen inside 
the egg membrane so that separate twins had been formed from one egg- 
Again it was sometimes observed that only part of the cleavage cells 
formed the blastula, the rest remaining as an irregular mass within the — 
‘Zeit. f. wiss. zool. 55, Dec., 1892. 
