594 INTEGUMENTARY SYSTEM 



the pigmentation of the bill is dependent upon the presence of the male sex 

 hormone (Domm, '39). 



e. Environmental Control of Chromatophoric Activity 



The above-mentioned instances of color-pattern development are concerned 

 with the elaboration and deposition of pigment within the epidermis and epi- 

 dermal structures. On the other hand, other observations demonstrate that 

 the contraction and expansion of chromatophores and, hence, the production 

 of different tones of color patterns, may be effected by a variety of environ- 

 mental stimuli in lower vertebrates. In some cases this may be due to direct 

 stimulation of the chromatophores by light or darkness or by changes in tem- 

 perature; in other instances the causative factor is a secretion from certain 

 glands, such as the pituitary or adrenal glands. The latter secretions in some 

 forms appear to be aroused by light waves to the eye, from whence the stimu- 

 lation is relayed through the nervous system to the respective gland or glands. 

 In still other instances the light waves to the eye may cause a direct stimulation 

 of the chromatophores by means of nerve fibers which reach the chromato- 

 phores. Other examples suggest that certain neurohumoral substances, elabo- 

 rated by the terminal fibers of the nerves some distance away from the chro- 

 matophore, slowly diffuse to the chromatophore, causing its expansion or 

 contraction (Noble, '32, pp. 141-147; Parker, '40). 



Bibliography 



Anthony, H. C. 1928; 1929. Horns and Dushane, G. P. 1943. The embryology of 



antlers, their evolution, occurrence, and vertebrate pigment cells. Part I. Am- 



function in the Mammalia. Bull. New phibia. Quart. Rev. Biol. 18:109. 



York Zool. Soc. 31; 32. . I944. xhe embryology of verte- 



Bardeen, C. R. 1900. The development of brate pigment cells. Part II. Birds. Quart, 



the musculature of the body wall in the Rev. Biol. 19:98. 



pig. Johns Hopkins Hosp. Rep. 9:367. Eastlick, H. L. and Wortham, R. A. 1946. 



Chandler. A. C. 1916. A study of the An experimental study on the feather- 

 structure of feathers with reference to pigmenting and subcutaneous melano- 

 their taxonomic significance. University phores in the silkie fowl. J. Exper. Zool. 

 of California Publ., Zool. 13:243. 103:233. 



Danforth, C. H. 1929. Genetic and meta- Engert, H. 1900. Die Entwicklung der 



bolic sex differences. J. Hered. 20:319. ventraien Rumpfmuskulatur bei Vogeln. 



Davies, H. R. 1889. Die Entwicklung der Morph. Jahrb. 29:169. 



Feder und ihre Beziehungen zu anderen Eycleshymer, A. C. 1906. The develop- 



Integumentgebilden. Morph. Jahrb. ment of chromatophores in Necturus. 



15:560. Am. J. Anat. 5:309. 



Dawson, A. B. 1920. The integument of Greene, C. W. 1899. The phosphorescent 



jVec/wrM5 macM/o5M5. J. Morphol. 34:487. organs in the toad-fish, Porkhthys no- 



Domm, L. V. 1939. Chap. V. Modifica- '"''"■ Girard. J. Morphol. 15:667. 



tions in sex and secondary sexual char- Harms, J. W. 1929, Die Realisation von 

 acters in birds in Sex and Internal Secre- Genen und die consecutive Adaption. I. 

 tions by Allen, Danforth, and Doisy. Phasen in der Differenzierung der An- 

 2d ed. The Williams & Wilkins Co., lagenkomplexe und die Frage der Land- 

 Baltimore, tier-werdung. Zeit. Wiss. Zool. 133:211. 



