38 



SCIENCE. 



[Vol. XI. No. 261 



yet failed to find any one who can readily detect the seven primary 

 colors. It is said of Dalton, from whom color-blindness was once 

 named, that he could distinguish only the colors of blue and yellow 

 in the solar spectrum. Dr. Mitchell tells of an officer who chose a 

 blue coat and a red waistcoat, believing them to be of the same 

 color ; of a tailor who mended a black garment with a crimson 

 patch, and put a red collar on a blue coat. Such mistakes seem 

 quite as ridiculous to me as to others. Yellow and black I have 

 never confounded with other colors. 



There is such a diversity in color-blindness, that it seems im- 

 possible to determine the cause. I am convinced that it is a 

 physical defect. The eye, as a mechanical instrument, has not 

 been found at fault. The cause is undoubtedly due to some 

 peculiarity of cerebral formation. Like the cause of left-handed- 

 ness, which is due to unusual development of the right brain, color- 

 blindness is due to a freak of nature. 



The education of the color-sense among the children of the 

 primary schools has proved of great value in removing that uncer- 

 tainty in distinguishing colors which of course may be found among 

 most ignorant people, old or young. This has its parallel in the 

 education of the ear to the appreciation of all the variations of the 

 musical scale. But for one v/ho is really color-blind, education 

 can be of little avail in correcting the defect. W. B. Harlow. 



Syracuse, N.Y., Jan. 27. 



A New Text-Book on Zoology. 



There can be no better evidence of the growing interest on the 

 part of certain reading-classes of all ages, and the importance that 

 is being dailj' attached to biological studies by school authorities 

 and educators, than the ever-increasing demand for good text-books 

 in zoology, and the frequency with which such volumes put in an ap- 

 pearance. We now have before us a thoroughly revised edition of 

 Steele's 'Fourteen Weeks in Zoology' (New York, Barnes), — a 

 little work that held its place with great popularity for ten years, 

 and which has now been almost entirely rewritten by Prof. J. W. 

 P. Jenks of Brown University, who is quite responsible for its 

 present form. 



From the author of the work I learn that the volume in scope is 

 principally designed for beginners in our high schools and acade- 

 mies at the average age of fifteen to eighteen years, in which schools 

 they have no special means for illustration. Moreover, to be effi- 

 cient as a text-book, it is intended to be used only by a class of 

 teachers who presumably possess quite a thorough knowledge of 

 general zoology, drawing, dissecting, zoological aids and appli- 

 ances, and kindred subjects. Taken as a whole, were this volume 

 placed in the hands of such a teacher, and its chief aim to be to 

 impart a notion of general zoology to a class of students of the 

 average age mentioned, after faithfully following out its chapters 

 for three or four months, we must believe that no better work has 

 yet appeared having a higher claim to such an end. Its pages are 

 crowded with beautiful cuts of the forms used in illustration of its 

 text, which cuts and illustrations have been for the most part ad- 

 mirably chosen ; and, notwithstanding its unavoidable brevity, the 

 subject-matter, as a rule, is presented in a manner calculated to in- 

 terest and instruct the student at every step. It seems to me, how- 

 ever, that even in a work of this character its author should add a 

 page to his preface, and explicitly state in words and figures and 

 acknowledge to whom he is indebted for his illustrations. We find 

 here numerous drawings of birds taken from Audubon and Wilson, 

 and many others, without a word of such acknowledgment, and 

 the oversight occurs throughout the work. We must believe that 

 even young academical students should be taught that this is not 

 the proper custom ; but where an author meets with such material 

 assistance, it should be duly noted. An excellent feature of the 

 work consists in properly dividing and accenting the technical 

 names to assist in their pronunciation ; while, on the other hand, a 

 serious defect is evidenced in the absence of a ' glossary of terms ' 

 at the end of the volume. 



In the main, the classification adopted shows the impress of re- 

 cent views in the premises ; but here, as much as anywhere else, it 

 needs the explanation of a skilled teacher, as the student would 

 gain but a very erroneous idea of the subject from this work alone, 

 as no family nor generic lines are drawn. Take, for example, the 



order Passeres, where lyre-birds, birds-of-paradise, finches, crows, 

 and larks, follow each other in the order I have given them, with- 

 out a single word of explanation as to their affinities. Then again 

 we find the author at total variance with the leading authorities in 

 placing the bats in the order Insectivora, without a word as to why 

 such a step should be taken. Nor will he meet with full support in 

 his order Biinana, containing only " one genus and a single 

 species," and that species having " the rank of a bemg who is alone 

 declared to have been created in the image of God " (p. 277). We 

 have no scientific proof for this latter view. Beneath about half 

 the figures we find given in parentheses each one's proportionate 

 size as compared with the living subject : we regret that this excel- 

 lent idea was not carried out through the entire work, and it will 

 be well for future text-books in zoology to adopt this plan. Writ- 

 ten, as the author of this work declares it is, for a class of students 

 as late as eighteen years of age, to my mind it exhibits another 

 thoroughly fatal omission, for it has not a word to say of that great 

 universal law pervading all nature and the world, which explains 

 the very origin of organic forms and the relations of the living ones 

 to those now extinct. Should a young man of eighteen years of 

 age complete the course pointed out by this work, and yet be igno- 

 rant of the law of evolution, I hold his zoological studies have 

 been but poorly grounded. A companion work to the one under 

 consideration on physics would be in the same case, had it omitted 

 the law of gravitation. 



The object of a text-book in zoology for a class of students from 

 fifteen to eighteen years of age should not have as its aim the en- 

 deavor to teach the greatest number of names of animate objects, 

 for at the present day that is a hopeless task, even were it a desir- 

 able end. It should, on the other hand, undertake to make clear 

 the general principles of biological classification ; it should by a 

 careful, detailed study of a few types, both vertebrate and inverte- 

 brate, clearly point out the universality of morphological laws, then 

 these two lessons should be combined ; next, it should be clearly 

 shown the relation between living and extinct types, and finally, by 

 a few clear examples, show the origin of certain forms, as the birds 

 from reptiles, and the ancestry of the horse, and so on ; all of which 

 is far more comprehensible than a jumble of isolated facts uncon- 

 nected by any known law. Such a course, properly expanded and 

 illustrated by a competent teacher, will give a student at once a 

 more intelligent appreciation of life and living forms ; make him a 

 better observer ; create in his mind a more healthy interest in the 

 subject; and finally send him forth with a kind of stimulation and 

 systematized knowledge which fits him to further pursue biological 

 research, should it happen in any given case to be imparted to the 

 mind of a student cast in the biological mould. 



R. W. Shufeldt. 



Fort Wingate, N. Mex , Jan. 9. 



The Flight of Birds. 



It is with great diffidence that I take part in a discussion partici- 

 pated in by such eminent authorities as Professor Newberrj' and 

 Professor Trowbridge, and it is with still more hesitation that I ven- 

 ture to disagree with any opinions brought forward by either of these 

 gentlemen. Nevertheless, I can but feel that undue stress has 

 been laid upon certain facts, while others of equal importance have 

 been overlooked or incorrectly stated. 



To a great extent the discussion hinges on the assumption that 

 birds need some mechanical device to relieve the muscles of strain 

 while soaring, — an assumption whose truth seems open to ques- 

 tion, as many of the lower animals are capable of automatic mus- 

 cular movements of very long duration. 



Among mammals the cetaceans are almost constantly on the 

 move both by day and by night, while others rest in positions that 

 seem to entail considerable muscular strain. Thus horses very 

 frequently sleep in a standing posture, and the skunk and baboon 

 have been observed to seek repose lying flat upon their backs, 

 with all four legs stiffly extended in the air ; a very good example 

 of unrelieved muscular strain may be seen in the tail of the spider- 

 monkey, whose prehensile power is sufficient to sustain the animal 

 after life is extinct ; some birds, during their migrations, fly or swim 

 for immense distances without stopping for rest, and there is very 

 good reason for believing that many of the petrels keep on the 



