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formalin. Stronger solutions may also be used, but they are likely to cause 
shrinkage. The solution should be changed after 24 hours except in amphi- 
bian eggs. Some collectors pour enough 100 per cent formalin into water 
containing amphibian larvae or eggs to make the solution approximately 
3 per cent or slightly more. Reptile eggs, at least, should be measured before 
preserving. The development of frog’s eggs and tadpoles may be staged 
according to the tables in Gosner (1960). 
Figure 45. Shell of western painted turtle showing where cuts should be made to 
remove plastron or lower shell. 
Preserving Skin Colour 
Frogs. The pigments in the skins of amphibians are relatively unstable, 
and when the animals are placed in the more common preservatives such as 
formalin and alcohol, the colours, particularly the more delicate tints, are 
either entirely lost or greatly altered. The following method for preserving 
amphibian skin colours is from Kincaid (1948), as summarized by Anderson 
(1960) and modified from papers by Juszczyk (1952) and Turner (1959). 
The method is to skin the frog and mount the skin on a sheet of heavy paper 
or cardboard. 
Frogs for this purpose are best killed with chloroform, as ether causes 
hemorrhage and resulting discoloration. The skin is slit along the middle of 
the underside from the anal area to the tip of the lower jaw, taking care not to 
cut the tissues beneath. Transverse cuts are made from the edge of the 
original cut across the underside of the forward portion of the body following 
the contour of the ventral side of the fore limbs, including the skin on the 
digits. Similar cuts are made to expose the under surfaces of the hind limbs 
with their digits. Very little effort is now required to loosen the skin from 
the underlying tissues. The contact with the anal area may require a snip of 
the scissors, and there may be some resistance when the skin is pulled over 
