$A$ : The scrotum acts as temperature regulator for the testes.
$R$ : Wall of scrotum is supported by dartos muscles which help in positioning of testes.

Eggs of reptiles and birds are

$A$ : The first sign of growing foetus may be noticed by listening to the heart sound through the stethoscope.
$R$ : By the end of second month of pregnancy, the foetus develops limbs and digits.

Egg of rabbit and man are

True coelom develops as a split in