February 3, 1888.] 



SCIENCE. 



57 



were made, give a higher percentage of success than the Signal 

 Service predictions for this vicinity. Professor Hazen made the 

 predictions for the Signal Service during October ; and if more ex- 

 tended comparisons between his predictions and those of Blue Hill 

 are of importance, why not compare the Blue Hill predictions with 

 the similar predictions of the Signal Service, published in the same 

 newspapers? The Blue Hill predictions were made for south- 

 eastern New England, and I am perfectly willing that they should 

 be verified for the States of New Hampshire, Massachusetts, and 

 Rhode Island in accordance with the published rules of the Signal 

 Office (see chief signal-officer's report for 1886). In making the 

 Blue Hill weather (not temperature) predictions, the phraseology 

 and definitions of the Signal Service have been closely followed ; 

 and, if any of the readers of Science care to extend the comparison, 

 I will gladly furnish them with the past or future Blue Hill predic- 

 tions as they appear in the Boston papers, since I am confident that 

 these, when verified in accordance with the published Signal Ser- 

 vice rules, will give a higher percentage of success than the predic- 

 tions of the Signal Service. When it is considered that the Blue 

 Hill predictions are extended for nine hours longer in advance 

 than those of the Signal Service made from the same telegraphic 

 reports, and that less than one-third the telegraphic data at the 

 command of the Signal Service are available at Blue Hill, it seems 

 clear that by improved methods and more localized predictions the 

 efficiency of the Signal Service could be greatly improved and its 

 expenses reduced. During January the Blue Hill predictions will 

 average something like fifteen to twenty per cent higher than the 

 Signal Service predictions for this locality ; and this seems of in- 

 terest, since I understand that Professor Hazen, who is assumed to 

 be one of the leading predicting-officers, made the Signal Service 

 predictions for this month. H. Helm Clayton. 



Blue Hill Observatory, Jan. 30. 



Hybrid Diseases. 



In a paper presented at the recent meeting of the American Pub- 

 lic Health Association {Scieiice, x. 289), Dr. E. M. Hunt of the New 

 Jersey Board of Health brings out some original ideas about 

 disease-germs, that are likely to prove misleading to persons whose 

 knowledge of the subject is derived from the public press. The 

 etiology of so many zymotic diseases is now under investigation by 

 experts in bacteriology, that the general reader or practitioner who 

 is not an investigator is severely taxed to keep track of the often 

 conflicting and incomplete results ; and an especial effort should 

 be made to avoid unnecessary complication of the subject by the 

 introduction of theories not based on a correct understanding of 

 what is known or extremely probable. 



Excluding the protozoan claimed by Laveran and others as the 

 cause of malarial fever, the moulds that occur in connection with 

 certain local diseases of the ear, etc., and the Actinomyces of man and 

 some other mammals, the active agents of common parasitic dis- 

 eases that are at all credited are bacteria. One of the systems of 

 classification now generally used recognizes four main divisions of 

 lower plants below mosses and liverworts, — thallophytes, zygo- 

 phytes, oophytes, and carpophytes, — beginning with the lowest. 

 Bacteria fall by common consent into the first and lowest of these 

 groups, — the protophytes. This group is a sort of onmiiim 

 gatherum for many things that cannot be placed elsewhere, and 

 is chiefly known by negative characters, the absence of much 

 evident structural differentiation, and of any form of sexual repro- 

 duction, heading the list. This being the case, it would partake of 

 dogmatism to make any very emphatic assertions about the plants 

 that now find lodgement in it ; yet it may fairly be said that no theory 

 that rests upon the assumption of sexual processes in any of the 

 protophytes is tenable. Hybridity is usually the result of sexual 

 union between representatives of two more or less nearly related 

 species, and in this sense is not only not known among plants of 

 this group, but very improbable, since they have thus far given the 

 best investigators no indication of even the simplest form of sexual 

 union, — conjugation. The only other mode of hybridizing, if it 

 really be such, corresponding to the formation of ' graft-hybrids ' 

 among flowering plants, could come only from the fusion of indi- 

 viduals of two species, and would amount to conjugation. It 

 seems to me, therefore, that such a theory of hybrid diseases as 



Dr. Hunt has propounded is entirely untenable, and a very unfor- 

 tunate addition to a literature already overcrowded with notions 

 that others must eliminate. 



I fear that my friend Mr. Meehan wrote his opinion on lichens 

 rather hastily, and perhaps without intending to have it given to 

 the readers of Science, or he would scarcely have expressed the 

 belief "that all lichens are hybrids between fungi and alga;." 

 Botanists do not agree on the lichen question, any more than 

 physicians do on the germ-theory of disease ; but neither the fol- 

 lowers of Sch wendener, nor the old school, would be likely to advocate 

 the hybridity that Mr. Meehan believes to be conceded. The rela- 

 tionship of the two parts of a lichen, according to the Schwendener 

 school, is merely that of association, either parasitic or symbiotic, 

 and in no sense comparable to hybridization, while the advocates 

 of lichen autonomy hold them for parts of one and the same indi- 

 vidual. 



Realizing fully the advisability of excluding dogmatism from the 

 discussion of all that pertains to sanitation, I have written this 

 correction in no ex cathedra spirit, and I trust that it will not ap- 

 pear to either Dr. Hunt or Mr. Meehan as any thing more than an 

 effort to check the entrance of error into the discussion of one of 

 the most important subjects that is prominently before the public. 



William Trelease. 



St. Louis, Mo., Jan. 2S. 



Color-Blindness. 



Referring to your comment in Science of Jan. 27, I would say 

 that I have always believed that the defect of color-blindness could 

 be accurately described only by one who, like myself, is subject to 

 the peculiarity. Frotn an early age I have been aware of the 

 trouble, and by my attempts to assign names to colors have often 

 furnished my friends n-vuch amusement. I have made many efforts 

 to correct the defect, and am convinced that any attempts to edu- 

 cate the color-sense will result in no benefit to those who are really 

 color-blind. 



There are two sets of colors which in my mind will always be 

 hopelessly confused. The greens, browns, and reds comprise the 

 first ; and the blues, pinks, and purples, the second. None of these 

 colors seem to me absolutely alike. The contrast, however, is not 

 striking, and I should describe each of the three as different shades 

 of the same color. 



Being near-sighted, I could not at a distance distinguish the 

 blossoms from the leaves of a bed of scarlet geraniums. On ap- 

 proaching, however, I could readily detect the difference, but should 

 describe the flowers as darker than the leaves, though to my eyes 

 somewhat similar in color. While riding through the fields of 

 France, members of our party frequently exclaimed at the multitude 

 of scarlet poppies in the grass. Though I looked with longing 

 eyes, not a poppy did I see during the entire journey. Similarly I 

 am unable to detect cherries upon the trees, or strawberries on 

 their vines, unless quite near to them. Notwithstanding this con- 

 fusion of green, red, and also of brown, I can, by the worsted test, 

 detect a difference in all the shades of these three colors. If I at- 

 tempted to assign names to the various hues, it would of course be 

 mere guess-work. The neutral tints of a November landscape, 

 too, possess great beauty for me. The green of the grass, the 

 browns of the leafless trees or of the soils in adjoining fields, the 

 sombre hues of the sky, are all pleasing to my eye. Such being 

 the case, the term ' color-blindness ' seems altogether a mis- 

 nomer. 



The second set of colors I should describe as follows : pinks, 

 blues, and purples are closely allied ; I should call them all blue. 

 Pink seems a lighter, and purple a darker, shade of the same hue. 

 But, as in the case of the first set, all variations of these three colors 

 are readily manifest to my eye. 



It may seem too strange to be true, but I have frequently ar- 

 ranged flowers into bouquets which have been perfectly satisfactory 

 to those who are not color-blind. I have, of course, no means of 

 determining whether a briUiant sunset is more charming to others 

 than to myself. I fancy that my defect deprives me of very little of 

 its beauty. 



Although in the rainbow I can distinguish only the red, yellow, 

 and blue, it is probably as attractive to me as to others. I have as 



