有沒有動物的胚胎不在母體生長

海賊
鴨嘴獸
針鼴

有。

Refer to wikipedia:
Most mammals belong to the placental group. The four largest orders within the placental mammals are Rodentia (mice, rats, and other small, gnawing mammals), Chiroptera (bats), Carnivora (dogs, cats, bears, and other mammals that primarily eat meat), and Cetartiodactyla (including numerous herbivore species, such as deer, sheep, goats, and buffalos, plus whales).

--> Most 即係唔係所有啦~



動物例子:
鴨咀獸

其他less common 的例子:
http://www.answers.com/topic/list-of-monotremes-and-marsupials