NIGG3RS, or placenta
If the animal comes from an egg it will get its nutrients from the yolk. If it is a mammal it will get it from the umbilical cord.
yolk
It's a sack and not an egg but the primary food source, the only one, is the placenta and the nutrients go via the umbilical cord.
A developing mammal inside of the mother.
I believe it is called an embryo
A developing chick nourishes itself inside the eggshell through the egg yolk. This is the chicks source of food.
An egg yolk is the part of an egg which serves as the food source for the developing embryo inside.
what is the source of nourishment for developing fish embryos?
A mammal embryo is the developing baby inside the mother.
Gilbert's Potoroo is a small mammal which lives in Western Australia in a restricted habitat, with a restricted food source. It was believed to be extinct from the early 1900s, but its recent rediscovery has led to the development of a recovery plan.
The platypus is one mammal which must eat its own weight in food each day.
A placental mammal.