565 
en 
| 41/, m.gr. uranium-| 17 m.gr. uranium- | 29!/, m.gr. uranium- 
nitrate pro L. nitrate pro L. nitrate pro L. 
June 26th | 5.5—10 m.m. 5— 9.8 m.m. 5 —7.5 m.m. 
July 10th 6 —11 m.m. 5-10 mm. 4.5—9 m.m. 
July 30th 7 —11 mm. 6— 9.5 m.m. 5 —10 m.m. 
August 14th 9.5 m.m. 
August 24th 10.5—11.5 m.m. 
September 3 12 m.m. ) front-limbs (10.2 mm. front-limbs 
Cae Konin 
September 14th | 11 m.m.§ reduction | 8.4 m.m.9 reduction | 8.5—9.6m.m. (frontl.) 
November 27th 10 m.m. 11 m.m. 8—11.8 m.m. 
poles are all the smaller in proportion as the quantity uranium- 
nitrate is greater. The following gives a more detailed account. 
a. 41/, mgr. uranyl-nitrate pro Liter. 
On June 26th and July 10th the measurements are as mentioned; the biggest 
tadpoles only have an indication of hind limbs. On July-20th the biggest tadpoles 
have hind limbs which do not lie any more straight along the tail, but which are 
abducted. On August 14th it was the first time that front limbs broke through 
with one tadpole of 9.5 mm ; on Sept 3rd. and Sept. 14th the first tail-reductions 
were observed. On November 27th the last tadpole of 10 min. with small hind 
limbs, showing signs of diminishing vitality, was killed and fixed. 
6. 17 mgr. uranyl nitrate pro Liter. 
From April 14th till July 10th the growth makes very little progress, the 
maximum length only being 10 mm ; tiny little points of hind limbs are present, 
and it is not before July 30th that one tadpole has hind limbs in abduction; on 
September 3rd. the first tail-reduction is observed. On November 27th the last living 
tadpole has a length of 11 mm. 
c. 29'/ mgr. uranyl-nitrate pro Liter. 
The growth.still goes more slowly than the preceding ones. On July 80th I see 
tadpoles with points of hind limbs. The beginning of tail-reduction was observed 
for the first time on September 7th; after that regularly; the size of the tadpoles 
then being 9,6—11,5 mm. On November 27th the last two tadpoles of 8.5 and 
11 mm. were fixed. 
Il. In different periods of the development tadpoles were taken 
out of the uraniam solutions and put into ordinary water. It then 
appeared that almost immediately the development took place much 
more quickly than with the tadpoles that remained in the uranium- 
solution; it must be well understood that the piscidine-tadpoles grew 
more quickly than the rice-tadpoles. 
