To our dismay, we saw that there were snails everywhere: they had escaped from the paper bag and had taken complete possession of the hall! I have never been able to look at a snail since then.

　　19.To our dismay, we saw that there were snails everywhere: they had escaped from the paper bag and had taken complete possession of the hall!

　　使我们惊愕的是门厅里到处爬满了蜗牛：它们从纸袋里逃了出来，爬得满厅都是!

　　语言点:句子结构分析:that之后的内容是saw的宾语，即that引导一个宾语从句;冒号后面的内容是对冒号前面的句子进行进一步的解释说明。

　　20.I have never been able to look at a snail since then.

　　从那以后，我再也不能看一眼蜗牛了。

　　语言点:句子结构分析:be able to do sth.的意思是“能够做某事”。Since then放在句尾，有加强语气的作用。