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of natural selection having been concerned in the process and so the proof is not conclusive. A striking case is given by Mr.Gadow in the Proc.Royal (illegible text)
Inst..Academy (Vol.II.No.2). He there describes the Crop and Sternum of Opi
esthocomus. This bird has a peculiar alimentary canal, the gizzard is much reduced in size and strength and the function usually performed by it has been assumed by another organ, the Crop which has consequently also become modified in a peculiar fashion. The wide and thick-walled crop rests directly upon the breast-bone. This has resulted in the (illegible text)
destruction of the skeleton parts of the bird such as the recession
secession of the heel
(illegible text) and the depression of the (illegible text)
(illegible text). An examination of the embryo proves that these changes take place at an early date. With regard to the ontogenetic development Mr.Gadow says that "the crop assumes its peculiar shape at a very early period, certainly long before it can be functional". And, again, he adds "although we see that, and
^ how the crop, by its downward growth, gradually encroaches upon and modifies the conformation of neighbouring organs, some of these modifications of the sternal apparatus are already (illegible text)
performed to a considerable extent, before they are actually necessitated. They are (illegible text)
unbounded." He concludes that "the embryonic development of the Hoazin
(illegible text) shows a faithful, but slightly condensed, repetition of those changes which its ancestors have acquired through adaptation to a peculiarly isolated life and diet".