Abstract

Skin-grafting experiments have been performed on the appendages of Rhodnius and Triatoma. The formation of folds of cuticle and a changed orientation of the bristles after moulting were used as criteria for incompatibility. Grafts which did not cause these changes were said to ‘take’. Grafts implanted in a way which disturbs the relative position in the axis of the segment do not take. Grafts moved around a segment take. Grafts between different segments of appendages take, provided they occupy similar positions in the axis of the segment. Grafts between the same segment in different appendages also take, provided they are in similar relative positions in the axis of the segment. The results are consistent with there being a gradient repeating in segmental appendages in a way comparable to that postulated to exist in the abdominal segments. The parallel between the gradient described here and the ‘prepattern’ concept derived from genetics is discussed.

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