370 KING. [Vou XIX. 
September. In order to compare the development of the 
ova in the young toad with that of the ova in the adult, por- 
tions of the ovaries of mature females were preserved at 
different times during the summer months. As the eggs ap- 
pear to develop along similar lines in all toads, ovaries of 
young females were used principally for these investigations, 
since in them the ova are more nearly uniform in size than 
they are in the adult, and in a single section it is possible to 
find a large number of eggs in practically the same stage of 
development. 
The very conflicting results that have been obtained by the 
investigators who have studied the development of the germ- 
cells in amphibians can doubtless be attributed, in part at 
least, to the great diversity of ways in which the material 
has been preserved. Carnoy and Lebrun, who have studied 
the germinal vesicle in the eggs of many different species of 
amphibians, unhesitatingly recommend Gilson’s fluid as the 
best fixative for the amphibian egg. I have not found that 
this liquid gives a satisfactory fixation of the egg of Bufo, 
as it usually causes a decided shrinkage of the nucleus and, 
at certain stages, a distortion of the nuclear contents. A 
number of different fixing fluids have been tried during the 
course of these investigations, among which may be mentioned 
Zenker’s fluid, corrosive-acetic (5 per cent acetic acid), cor- 
rosive-formalin (Bouin’s method), picro-acetic, Flemming’s 
solution, chromic-acetic, and Hermann’s fluid. Flemming’s 
solution (strong formula) is the best fixative for the odgonia 
and the early growth stages of the odcytes, although Zenker’s 
fluid and Hermann’s fluid give very good results. After the 
yolk has formed Flemming’s solution does not penetrate the 
egg sufficiently well to give a satisfactory fixation. For this 
later period I have found that the chromic-acetic solution 
recommended in a previous paper (King, 49) gives the best 
preparations. Corrosive-acetic acid is also a good fixative for 
the egg at this period of its development, but it is especially 
valuable for the maturation stages. Corrosive-formalin and 
Picro-acetic do not give a satisfactory fixation of the egg of 
Bufo at any stage of its development. 
