. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. Chromatophores and Color Change 685 the state oF the chromatophore system of animals is hght, and in the great majority of animals the method of action of the light invokes principally the eyes, central nervous system, and \arious types of efferent pathvva\s, ner- \'ous, hormonal, or both. The importance of the eyes is clearly manifested in observing the immediate cessation, or great change in character, of color changes on the blinding of the animal. Color changes which are controlled by way of the eves are kno
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. Chromatophores and Color Change 685 the state oF the chromatophore system of animals is hght, and in the great majority of animals the method of action of the light invokes principally the eyes, central nervous system, and \arious types of efferent pathvva\s, ner- \'ous, hormonal, or both. The importance of the eyes is clearly manifested in observing the immediate cessation, or great change in character, of color changes on the blinding of the animal. Color changes which are controlled by way of the eves are known as secondary responses, in contrast with pri- mary responses, which are those proceeding under the influence of light through routes other than the eyes. The latter may involve either a direct action of light on the chromatophores or an influence of light operating re- flexly on the chromatophores through extra-ocular receptor mechanisms. Secondary color changes dominate the situation in most adult animals. Through a wide range of light intensities these changes do not result from changes in the total quantity of light striking the eye, but rather they are determined by the values of the ratios of the amount of light directly strik- ing the eye from above to die amount of light reflected from the background on which the organism resides. On an illuminated black background where. 90 I 80 0 s e 8 70 - , 0 o §60 - 0 J c E S ^50 •te - e a 0 I40 B 0 8° e CP a ""a 1 8 30 - _i 1 1 .. 1. 1— , Logarithm of liqhr intensitu Incident intensittj Vetlectid intensity A B Fig. 260. A, Relationship between the log of the incident Hght intensitj' and the average diameter of the melanophores of the minnow, Ericyinha. B, Relationship between the ratio of incident intensiiy to reflected intensity striking the eye and the average melanophore diameter. From ;' the ratio is large, the animal becomes dark, and on an illuminated white background where the ratio is small, th
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