Look at the many outlying islands round a continent, and see how many of their inhabitants can be raised only to the rank of doubtful species.

看看一个大陆周围的许多离岛， 看看有多少居民只能被提升到可疑物种的等级。

Excluding such cases of abrupt variations, the few which remain would at best constitute, if found in a state of nature, doubtful species, closely related to their parental types.

排除这种突然变异的情况，如果在自然状态下发现， 剩下的少数最多只能构成与它们的亲本类型密切相关的可疑物种。