Theories and facts as to palaeogenesis in its probable influence on the coloration of animals / by Jonathan Hutchinson.

  • Hutchinson, Jonathan, Sir, 1828-1913.
Date:
1912
Catalogue details

Licence: In copyright

Credit: Theories and facts as to palaeogenesis in its probable influence on the coloration of animals / by Jonathan Hutchinson. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    stood that the “ pattern ” implies much more than proneness to peculiarity in coloration. It depends upon modifications in structure which are inborn and inherited, and although capable of almost endless modifications and often suppressed as regards their manifestations are never entirely eradicated. It is to the possibility of their reappearance in remote generations or distant species that the word “ palseogenesis ” is useful. My chief object in the following pages is to show that there are certain recog- nisable tracts of skin common to all animals which have their own peculiar endowments. These latter are fundamental and receive in hereditary transmission modification only. Coloration—Elementary Observations. Amongst the elementary facts as regards the coloration of animals we may note first that the integument is patterned in two halves, which meet above and below, and which leave longitudinal streaks at what might be called their seams of junction. It is so common as to be almost universal that there is a streak down the middle of the back, beginning at the animal’s nose and extending to the tip of the tail. This dorsal streak may be narrow or broad, and may be almost endlessly diversified in tint, in size, and in details as to its formation, and by the interrup- tions to which it is liable. In many cases it is absolutely con- tinuous from nose-tip to tail-end, but in a great number it is interrupted by transverse bars or cut up into lozenges or spots. Very often it is indistinct or wholly concealed by growth of long hair. In some animals it is prone to peculiar forms of exaggera- tion either in its continuity or in parts. On the belly of the animal, from the tip of the lower jaw to the end of the tail, there is very usually a band of coloured hair which differs from the rest, but is seldom so well marked as the dorsal streak. It is usually much broader and less well defined than the latter, and very often it cannot be traced from beginning to end. In all cases both the dorsal and the abdominal streak should be looked for in young animals, or even in the foetus, as they are often obliterated as age advances. This abdominal streak becomes the “ linea fusca” in the observation of human beings, and is usually merely a pigmented band from epigastrum to pubes, but by no means infrequently grows coarse hair. In many animals it is with the adjacent parts of the belly white or lighter in tint than the rest. In connection with the dorsal and abdominal streaks theie may be developed, either other longitudinal ones running parallel to them at variable intervals, or vertical streaks coursing down the animal’s sides like ribs; and these bars may cross each other and may map out the skin into blocks more or less angular. Of these latter, the angle may often be destroyed, and