‘42 Miscellancous. 
On the Influence of Physico-Chemical Agencies upon the Development 
of the Tadpoles of Rana esculenta. By M. Emite Youne. 
The author subjected tadpoles just hatched to the action of saline 
solutions of various strengths. The salts employed were obtained 
by the evaporation of the water of the Mediterranean, and the larve 
were placed in solutions of 1, 3,5, 7, and 9 per 1000, which were 
renewed at the same time in all the vessels, and the whole were in 
other respects placed under precisely the same conditions. Asa 
general result, M. Yung states that the tadpoles are developed the 
more slowly the more considerable the degree of saltness of the water. 
In the solution of 2,5 no transformation took place, though some 
tadpoles lived long enough to acquire hind limbs. In a solution of 
71%, very young tadpoles die in a few hours; older ones survive 
for a few days. 
The author remarks upon the importance of placing equal num- 
bers of individuals in each vessel in experiments of this kind. On 
placing 4, 8, 12, 16, &c. tadpoles of the same age and the same 
brood in a series of vessels, and keeping them under precisely the 
same conditions, their development is found to be slower in proportion 
to the number living together, which confirms the results obtained by 
Semper for the Limnee. 
Finally, M. Yung subjected young tadpoles, which normally live 
in quiet water, to continuous agitation in a vessel containing two 
litres of water regularly renewed and suitable food. The agitation 
of the liquid was felt to the bottom of the vessel, but reached its 
maximum at the surface, where the tadpoles, on coming up to the air, 
had to struggle against strong waves. Under these conditions the 
eggs developed well; but the newly hatched tadpoles, being too 
feeble to seize their prey in so disturbed a medium, died of hunger, 
unless care was taken to give them daily a few moments of repose 
to take their food. The mortality was always greatest in the first 
few days ; it diminished immediately the first transformations were 
effected. Of twenty individuals placed in the vessel in April, eight 
have furnished little frogs, and on the Ist August only one had not 
completed its metamorphoses. 
If these agitated tadpoles be compared, at different periods, with 
others of the same brood developing in quiet water, it is found that 
the development of the former is slower (the test-tadpoles were all 
transformed on the 15th July), that they are less pigmented, which 
indicates bad nutrition (the tadpoles which do not eat much are 
always pale) ; and, lastly, that their tails are relatively more de- 
veloped, especially in width, which is explained by the greater use 
they are obliged to make of these organs in struggling against the 
waves.— Bibl. Univ., Arch. des Sciences, pér. 3, tome x. p. 347, 
October 15, 1883. 
