In the economy, we will say of a feline animal{467}, the feline structure of the embryo or of the sucking kitten is of quite secondary importance to it; hence, if a feline animal varied (assuming for the time the possibility of this) and if some place in the economy of nature favoured the selection of a longer-limbed variety, it would be quite unimportant to the production by natural selection of a long-limbed breed, whether the limbs of the embryo and kitten were elongated if they _became_ so _as soon_ as the animal had to provide food for itself. And if it were found after continued selection and the production of several new breeds from one parent-stock, that the successive variations had supervened, not very early in the youth or embryonic life of each breed (and we have just seen that it is quite unimportant whether it does so or not), then it obviously follows that the young or embryos of the several breeds will continue resembling each other more closely than their adult parents{468}. And again, if two of these breeds became each the parent-stock of several other breeds, forming two genera, the young and embryos of these would still retain a greater resemblance to the one original stock than when in an adult state. Therefore if it could be shown that the period of the slight successive variations does not always supervene at a very early period of life, the greater resemblance or closer unity in type of animals in the young than in the full-grown state would be explained. Before practically{469} endeavouring to discover in our domestic races whether the structure or form of the young has or has not changed in an exactly corresponding degree with the changes of full-grown animals, it will be well to show that it is at least quite _possible_ for the primary germinal vesicle to be impressed with a tendency to produce some change on the growing tissues which will not be fully effected till the animal is advanced in life. {467} This corresponds to the _Origin_, Ed. i. pp. 443-4, vi. p. 610: the "feline animal" is not used to illustrate the generalisation, but is so used in the Essay of 1842, p. 42. {468} _Origin_, Ed. i. p. 447, vi. p. 613. {469} In the margin is written "Get young pigeons"; this was afterwards done, and the results are given in the _Origin_, Ed. i. p. 445, vi. p. 612.