CORRESPONDENCE OF SKIN PIGMENTS IN RELATED 

 SPECIES OF NUDIBRANCHS. 



By W. J. CROZIER. 

 (From the Zoological Laboratory, Rutgers College, New Brunswick, N. J.) 



(Received for publication, October 21, 1921.) 



That pigmentary materials occurring in various species of certain 

 genera of marine invertebrates may be chemically very similar, or 

 even identical, has several times been suggested.^ In some cases the 

 presence of such chemically similar coloring matters, playing an 

 important role in determining the appearance of the animals, has a 

 distinct part in the theory of animal coloration, since, if substantiated, 

 identity of composition as regards pigments may be significant for 

 the evolutional origin of types of pigmentation {e.g. in so called 

 ''warning" coloration^) , The pigmentation of the large nudibranch 

 Chromodoris zebra has been studied from the standpoint of its possible 

 adaptive quality,^ and since it happens that coloring matters super- 

 ficially corresponding to those in Chromodoris zebra are found in a good 

 many species of this widely dispersed genus,^ it is desirable to examine 

 the degree of chemical similarity of these substances. The blue pig- 

 ment which plays a conspicuous part in the coloration of these crea- 

 tures has properties favorable for such study. A yeUow pigment, 

 also of frequent occurrence in the genus, belongs to the carotinoid 

 "lipochrome" series, but because of the very general occurrence of 

 such substances as pigmentary components derived from plant food, 

 it is less significant for the present purpose. 



• Briot, A., Compt. rend. Soc. Biol., 1906, Ixxxviii, 1157. Crozier, W. J., Zool. 

 Jahrb., Abt. Zool., 1915, xxxv, 233; /. Biol. Chem., 1918, x.xxv, 455; .Im. Naturalist, 

 Hi, 552. 



2 Crozier, W. J., Anat. Rec, 1919-20, vii, 349. 



3 Crozier, W. J., Anat. Rec, 1919-20, vii, 349; Proc. Nat. Acad. Sci., 1916, 

 ii, 672. 



* Crozier, W. J., /. Physiol., 1913-14, xlvii, 491. 



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