Mammal young often helpless and female provides nutrients and parental care. Young do not need to run risks attendant with foraging themselves. 3. modification of extra-embryonic membranes to form the ...

In studies of epithelio-mesenchymal interaction in cultured mouse embryo rudiments we have, recently employed so-called membrane or molecular filters 2 for similar purposes and have noted two ...

Amniotic egg appears very early in reptilian evolution. Egg has several special extra-embryonic membranes, which allow it to develop on land independent of water. Just as significant as evolution of ...

Scientists have observed a type of cell division in a prehistoric unicellular organism that resembles the embryonic ...

The amniotic sac, commonly called the bag of waters, sometimes the membranes, is the sac in which the embryo and later fetus develops in amniotes. It is a thin but tough transparent pair of membranes ...

In red, the membranes and in blue the nuclei with their ... to form complex beings. This embryonic development follows precise stages that are remarkably similar between animal species and could ...

A cell division resembling that of an animal embryo has been observed in a prehistoric unicellular organism, suggesting that embryonic development might have existed prior to the evolution of animals.