72 SUBSTITUTION OF A WING FOR A LEG IN A MOTH. 



happened had a larger portion of a second individual been 

 developed. 



There is a third explanation, which was the first that suggested 

 itself to my mind, but which, upon consideration, I rejected as 

 having absolutely no support from any other known case in the 

 animal kingdom. This is, that a substitution of a wing for the 

 normal leg has taken place ; that is to say, that that portion of the 

 embryo or larva which represents the left hind-leg in the perfect 

 insect, and which has in every other known instance grown or devel- 

 oped into a leg, has not done so in this case, but has, by some means 

 or other, become a wing. The chief, and indeed as far as I see, 

 only support of this theory is, that in plants petals very frequently 

 take the place of the stamens and pistil, as we see in the case of 

 double flowers. We often find stamens with the lower part very 

 broad and flat and the anther much diminished in size, and all 

 intermediate stages of development will occur on the same plant, 

 and, indeed, in the same flower, between the perfect stamen and 

 the perfect petal. But this kind of transformation is, so far as I 

 am aware, quite unknown in the animal kingdom, which seems 

 consistent with the far superior organisation of a leg or wing to a 

 stamen or petal, and when the apparent substitution can be 

 explained by a theory which is quite consistent with what is known 

 to occur amongst animals, and is founded on other cases of 

 monstrosity among them, I think it is wiser to adopt it, and not to 

 go for our parallel cases to plants, which are so totally different in 

 their nature and mode of growth. 



Even the change from stamen to petal in a plant is not, it seems 

 to me, a real case of substitution, as I am not aware that it has 

 been proved that the stamen in its earliest distinct stage, or embryo 

 stamen, if I may so call it, will grow into anything but a stamen, 

 or the embryo of the intermediate stamen-petal into anything else 

 but a stamen-petal; but it seems to me more likely that the 

 emliryo is formed by the growth of the plant, and that that organ 

 of which the embryo is produced will be subsequently developed, 

 and no other. 



