Stir the custard occasionally to prevent a skin forming.

Reptiles have placodes too. But in a reptile embryo each placode switches on genes that cause only the skin cells on the back edge of the placode to grow, eventually forming scales.

The fertilized female worm(s) (which measures from 60–100 cm long) migrates under the skin tissues until it reaches the lower limbs, forming a blister or swelling from which it eventually emerges.