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.

My reasons for doubting whether natural species have changed as abruptly as have occasionally domestic races, and for entirely disbelieving that they have changed in the wonderful manner indicated by Mr.

Mivart, are as follows.

According to our experience, abrupt and strongly marked variations occur in our domesticated productions, singly and at rather long intervals of time.