Chapter CLXXIII: Section 44: It has been suggested by very excellent people that these

resemblances are due to some unexplained necessity of adherence to type, as though, the power that they assume created these animals originally, as they are now, coupled creative ability with a plentiful lack of ideas, and so perforce repeated itself with impotent variations. On the other hand, we have the supposition that these are "family likenesses," and the marks of a common ancestry. This is the opinion now accepted by all zoologists of repute.