观察了不同动物的卵，小芸想根据有无硬壳给它们分类，请你帮助她完成连线。

鸡卵                                                                      有硬壳                                                                      龟卵

蛇卵                                                                      无硬壳                                                                      蛙卵

鱼卵                                                                      蚂蚁                                                                         卵