222 THE SNAKES OF SOUTH ?AFRICA. 
The young Puff Adders average seven inches in length at 
birth. They are venomous as soon as born, and will strike fiercely ; 
if irritated. Mice bitten by them died within a few minutes. I 
have made them bite full-grown rats, which died in half an hour. 
A friend was bitten on the hand by a young Puff Adder a day or 
two old. His arm swelled, and there was a good deal of con- 
stitutional disturbance, but he recovered in a few days. 
During April of 1910, five Puff Adders gave birth to young in 
the Port Elizabeth Museum. Three of the Adders brought forth 
the whole of the young alive. The other two gave birth to many 
fully-developed ones, as well as about a dozen only two-thirds 
Fic. 89.—(1) The egg of a Puff Adder. These eggs develop inside the snake, and lie in two long rows. They 
incubate within the body of the parent. (2) A young Puff Adder just born, but only partly developed. 
In the front is seen some of the egg still unabsorbed. The embryo is enveloped in a membraneous 
bag. (3) A young Puff Adder, fully developed, just born. It is struggling out of the transparent 
membraneous sheath in which it was born. Its headis protruding. (4) A young Puff Adder, half an 
hour after birth, 74 inches long. One hour after birth it bit a rat. The rat was dead in fifteen 
minutes. ° 
matured. I have frequently noticed on dissecting Puff Adders 
that the young are not always developed to the same degree. 
Sometimes the eggs fail to incubate. In this case they harden, 
and are sometimes passed out. In other cases they remain in 
the snake, and their presence eventually kills her. 
Puff Adders have given birth to young a great many times 
in our snake cages at the Port Elizabeth Museum during the 
months of March, April, and May. This would lead us to conclude 
that the development of the eggs and incubation period within the 
mother is about six or seven months, as the Puff Adders begin 
coming forth from their winter retreats mostly during October 
