The newly hatched silkworm can not come out with the head ahead, but on the contray, it comes out with the tail ahead when it comes out of the chorion, in case the loose-formed eggs are vibrated artificially, at the end of the incubation. So the newly hatched silkworm can not throw off the chorion alone which covers his head. This kind of eggs occurs about 30% when they are vibrated. In case they were raised, they could not grow well and some of them died. The result was quite bad. In conclusion, it would be better to distribute earlier the loose-formed eggs farmers and the loose-formed eggs must not be vibrated at the end of the incubation.