THE INFLUENCE OF SALT AND OTHER SOLUTIONS ON THE FROG. 175 
The Influence of Salt and other Solutions on the Development of the 
Frog.—Report of the Committee, consisting of Professor W. I. R. 
WELDON (Chairman), Mr. J. W. JENKINSON (Secretary), and 
Professor 8. J. Hickson. (Drawn up by the Secretary.) 
In the report presented to Section D at the Cambridge meeting in 
1904 an account was given of the development of the frog’s egg in a 
number of isotonic solutions of various substances. The substances 
employed were :— 
1. The chlorides of potassium, lithium, ammonium, calcium, magne- 
sium, barium, strontium, and sodium. 
2. The bromides of the same bases. 
3. The iodides of sodium, potassium, lithium, and ammonium. 
4. The nitrates of sodium, lithium, ammonium, potassium, magnesium, 
strontium, and calcium. 
5. The sulphates of sodium, lithium, ammonium, and magnesium. 
6. Cane sugar and dextrose. 
7. Urea. 
These substances were employed in solutions isotonic with a solution 
of sodium chloride—0°625 per cent.—which was known to produce a cer- 
tain distortion of development, and the object of the experiment was to 
ascertain whether the effects observed were due to the increased osmotic 
pressure of the medium or to some other cause. 
Since the publication of the last report the microscopical investi- 
gation—which was not at the time quite completed—has been brought to 
a conclusion, the experiments have been repeated and confirmed—in one 
or two points corrected—and some new experiments undertaken to throw 
light, if possible, on the same problem. The present report embodies :— 
I. A corrected résumé of the growth of the egg in the isotonic solu- 
tions referred to, to which potassium sulphate has been added. 
II. An account of the results of the fresh experiments. 
I. Solutions Isotonic with 0°625 per cent. NaCl. 
In the last report these solutions were divided into four classes, 
according to the effect produced. 
A, The egg dies in an early stage ; segmentation or gastrulation. 
This occurs with NH,Cl, SrCl,, BaCl,, CaCl,, NH,Br, SrBr,, BaBr,, 
CaBr., MgBr,, Lil,NH,I, KI, NH,NO;, Ca(NO3)., Sr(NO3)5. 
The liquefaction of yolk-granules, ascribed before to all these solutions, 
has been found not to occur in NH,I, Lil, KI, NH,Br, NH,NO,, or 
Ca(NO3)>. 
B. The egg loses its power of elongating, and remains nearly spherical ; 
differentiation of the germ-layers and of the organs of the embryo 
proceeds nevertheless. This effect was stated to be produced by KCl and 
LiCl, NaBr, KBr and LiBr, Nal, Li,SO, and (NH,),SO,, LiNO, and 
KNO,. 
1. It has been found that in sodium bromide development goes further 
