THE ADDER, 155 
larger and quite round, the embryo being seen through 
the covering membrane lying on the egg surface. The 
embryos were 34 inches long, and, except im size, were 
much like those of July 10. 
A dissection a fortnight later shows still more rapid 
progress, and by August 13 the embryos look like 
young adders for the first time. 
Even through the ege-membrane 
the markings could be distin- 
guished, the egg being the one 
reproduced here. The embryos 
in this adder were again ten in 
number, and it was surprising 
on measuring them to find they 
were 5 inches in lencth I | |. 
Fra. 36.— Ea or AppER. 
photographed three of them, 
with a scale of inches marked on the dish (fig. 37), 
which gives a very good idea of the size and general 
appearance. 
The anterior abdominal wall was now completely 
closed. The colour of the belly surface was still 
whitish, but the division where each seale was to 
appear was evident. The colour shaded off into erey 
on the back, and the markines were distinet, the zig- 
zag line and the extra line of patches opposite each 
point of the zigzag both quite plainly visible. 
There is one very interesting detail in connection 
with the development of the markings which is seen 
at this stage. Itis this. At the posterior part of the 
