In a fetal pug, just like in all other mammals, the placenta is responsible for removing nitrogenous wastes from the blood.

Here's why:

* Fetal kidneys are not fully functional: The fetal kidneys are still developing and are not yet capable of filtering and removing waste products from the blood effectively.

* Placenta takes over: The placenta, which is connected to the fetus through the umbilical cord, acts as a filter. It removes waste products, including nitrogenous wastes like urea, from the fetal blood and transfers them to the mother's blood. The mother's kidneys then filter and excrete these wastes.

So, while the fetal pug's own kidneys are developing, the placenta acts as a temporary "kidney" to maintain a healthy environment for the growing fetus.