August 21, 1914] 



SCIENCE 



283 



portions of specimens exposed more than four 

 weeks to the direct rays of the sunlight proved 

 most satisfactory. They exhibited all the 

 stages of pigment formation suggested by the 

 various theories, epidermal cells in which the 

 pigment was densest around the nucleus with 

 the nucleus in a shrinking condition, eon- 

 firming the theory of Jarisch and others; 

 further intercellular pigment masses with 

 amceboid processes situated between mucous 

 cells and glands similar to the melanoblasts 

 observed by Becarri and Brinkmann. Also 

 pigmented masses along the blood vessels of 

 the gills undoubtedly stimulated by the 

 respiratory changes in the circulation of the 

 blood, but the largest pigment mass consisted 

 of innumerable spherical bodies of accumu- 

 lated melanin granules which covered the 

 epidermis of the mantle and were held by a 

 layer of mucus exuded from the cells and 

 forming the ultimate fate of the pigmentation 

 process. In specimens that had been returned 

 to the dark after several weeks most of the 

 pigment had disappeared, and where present 

 was confined to the original pigment cells of 

 the epidermis, largely along the mantle edge, 

 with scattered disintegration products of pig- 

 ment granules throughout the epidermis. 



Though the work is still tentative, I have 

 come to the conclusion that animal pigmenta- 

 tion is probably a protein formation due to an 

 enzyme which is circulating in the blood and 

 present in the nucleoplasm of all secreting 

 cells. This, of course, could only be proved 

 by chemical analysis. In some cases the 

 leucocytes are transformed into specific ehro- 

 matophores or melanoblasts, capable of 

 amosboid motion; in others the deposition of 

 pigment has become a hereditary factor, as, 

 e. g., in the choroid coat of the eye or the ink- 

 bag of the squid; in still other oases pigmenta- 

 tion is stimulated into action by internal 

 metabolic processes as well as by external 

 conditions of light, temperature and atmos- 

 pheric gases. In the case of the oyster light 

 is the chief factor in the stimulation of pig- 

 ment, which is the result of protective reaction 

 against abnormal conditions. But this re- 

 action is in my judgment not merely chemical. 



it is preeminently biological and under the 

 control of nuclear determinants. 



e. c. sohiedt 

 Franklin and Marshall College, 

 Lancastek, Pa. 



SPECIAL ARTICLES 



SUPPRESSION AND LOSS OP CHARACTERS IN 

 SUNFLOWERS 



Helianihus and GEnoihera are very little 

 related, yet in breeding and studying sun- 

 flowers one is constantly reminded of phenom- 

 ena previously recorded in connection with ' 

 evening primroses. The parallelism in varia- 

 tion is such that one is led to ask, what, pre- 

 cisely, do we mean by a " new " variation ? 

 A " new variety " can be easily defined as a 

 distinguishable type arising in a species, and 

 either " new " in the sense of being newly dis- 

 covered, or (as we believe to have been true 

 of the red sunflower) actually originating 

 within the period of our knowledge. We have 

 thought it highly satisfactory to be able to 

 list^ instances of newly occurring varieties or 

 mutations, with some suggestions regarding 

 their proximate causes, but it must not be for- 

 gotten that in so doing we have gone only a 

 little way below the surface. If many plants, 

 of widely different families, produce entirely 

 analogous variations, it must be true that there 

 is something in the constitution of the whole 

 series which makes the apparent accidents 

 inevitable. One is reminded of the occasion 

 when Whistler made an exceptionally good 

 joke, and Oscar Wilde, who was present, re- 

 marked, "I wish I had made that joke!" 

 Whistler replied, " My dear fellow, don't worry, 

 you will make it." So might the Gaillardia 

 have said to the sunflower, five years ago, 

 though without the sarcastic intent. 



The commonest of all variations results from 

 the loss of a character, but this may be due to 

 latency, or to the dropping out of a determiner. 

 In sunflowers, the " primrose " varieties, with 

 pale primrose-colored rays, offer a typical case ; 

 another, of which a single example occurred in 



1 Gates, Quart. Jour. Micr. Science, Feb., 1914, 

 pp. 562-563, gives an excellent tabulation of the 

 principal types of mutation. 



