In mammals,the relaxin hormone is secreted by:

The gestation period in human beings is about:

The first sign of the growing foetus may be noticed by listening to the heart sound carefully through the stethoscope. The embryo's heart is formed . . . . . . .

Which one of the following is derived from the ectoderm?

Assertion : After ovulation,the Graafian follicle transforms into corpus luteum.
Reason : The corpus luteum secretes a large amount of progesterone.

The longest gestation period among the given options is found in