March 24, 1893.] 



SCIENCE. 



165 



■claim that species do not originatf' noic in a state of nature, 

 would certainly find it a difficult ta^k to refute or explain on any 

 Taut one hypotliesis the facts given by our author. One case in 

 particular is of great interest. It would appear that two butter- 

 flies, species of Heliconms. are extremely abundant in the forests 

 along the river. They inhabit, however, different sections of the 

 country, one of which in moister than the other. One species 

 occurs in the dry forests, the other in the moister ones. One 

 species, H. melpomene, is black with a large crimson spot on its 

 wings ; the other is H. thelxiope, in which the wings are beauti- 

 fully rayed with black and crimson and have a number of bright- 

 yellow spots. Both have the same habits, and they have long 

 been regarded as perfectly distinct species. We quote now Mr. 

 Bates's words: ''There are, as might be supposed, distrirts of 

 forest intermediate in character between the drier areas of Obydos, 

 etc., and the moister tracts which compose the rest of the immense 

 river valley. At two places in these intermediate districts, . . .. 

 most of the individuals of these Heliconii which occurred were 

 transiiion forms between the two species. Already, at Obydos, 

 H. melpomene showed some slight variation amongst its individ- 

 uals in the direction of H. thelxiope, but not anything nearly ap- 

 proaching it. It might be said that these transiiion forms were 

 hybrids, produced by the intercrossing of tvs'o originally distinct 

 species; but the two come in contact in several places where 

 these intermediate examples are unknown, and 1 never observed 

 them to pair with each other. . . . These hybrid-looking speci- 

 mens are connected together by so complete a chain of gradations 

 that it is difficult to separate them even into varieties, and they are 

 incomparably more rare than the two extreme forms. They link 

 together gradually the wide interval between the two species. 

 One is driven to conclude, from these facts, that the two were 

 ■originally one and the same; the mode in which they occur and 

 their relative geographical positions being in favor of the suppo- 

 sition that H. thelxiope has been derived from H. melpomene. 

 Both are, nevertheless, good and true species in all the essential 

 characters of species; for, as already observed, they do not pair 

 together when existing side by side, nor is there any appearance 

 of reversion to an original common form under the same circum- 

 stances." 



We have already so far overstepped our space that we must 

 reluctantly refrain from quoting further. We would, however, 

 call particular attention to the account given of Termites on pages 

 209-214; that on Fire Ants on page 227; on Monkeys on pages 

 33 1-345; and on the general features of ant life on pages 855-363. 

 The remarks upon floating pumice on pages 263-264 are well 

 worthy the consideration of students of geographical distribution, 

 and those on page 169 are commended to the student of compara- 

 tive' philology, as indicating a method of the formation of dialects 

 among savage tribes. 



One word more and we have done; for even at the risk of tiling 

 the patient reader we add one more quotation. After a life of 

 eleven years spent in the Amazonian forests, certainly Bates was 

 well qualified to judge between that life and civilized man's. He 

 had formed a love for the country, and he took leave of it with re- 

 gret. The desire, however, of once again seeing his parents and of 

 enjoying the pleasures of intellectual society drew him from this 

 "Naturalists' Paradise." "During this last night on the Para 

 River," he says, "a crowd of unusual thoughts occupied my mind. 

 Recollections of English climate, scenery, and modes of life came 

 to me with a vividness 1 had never before experienced during the 

 eleven years of my absence. Pictures of startling clearness rose 

 up of the gloomy winters, the long, gray twilights, murky atmos- 

 phere, elongated shadows, chilly springs, and sloppy summers; 

 of factory chimneys and crowds of grimy operatives, rung to 

 work in early n)0rning by factory bells; of union workhouses, 

 confined rooms, artificial cares and slavish conventionalities. To 

 live again amidst these dull scenes I was quitting a country of 

 perpetual summer, where my life had been spent, like that of 

 three- fourths of the people, in gypsy fashion, on the endless 

 streams or in the boundless forests. I was leaving the equator, 

 where the well-balanced forces of nature maintained a land sur- 

 face and climate that seemed to be typical of mundane order and 

 beauty, to sail towards the North Pole, where lay my home, under 



crepuscular skies, somewhere about fifty-two degrees of latitude. 

 It was natural to feel a little dismayed at so great a change; but 

 now, after three years of rene>ved experience of England, I find 

 how incomparably superior is civilized life, where feelings, tastes, 

 and iiitellect find abundant nourishment, to the spiritual sterility 

 of half-savage existence, even if it were passed in the Garden of 

 Eden. What has struck me powerfully is the immeasurably 

 greater diversity and interest of human character and social con- 

 ditions in a single civilized nation than in equatorial South 

 Americi. where three distinct races of man live together. The 

 superiority of the bleak north to tropical regions, however, is 

 only in its social aspect; for I hold to the opinion that, although 

 humanity can reach an advanced state of culture only by battling 

 with the inclemencies of nature in high latitudes, it is under the 

 equator alone that the perfect race of the futui'e will attain to 

 complete fruition of man's beautiful heritage, the earth." 



Joseph F. James 



Text- Booh nf the Emhryology of Man and of Mammals. By De. 

 OscAE Hertwiq. Translated by Professor E. L. Mark. 

 New York, Macmillan & Co. $5.25. 



Professor Mark has done a great service to English science 

 by translating this text-book of embryology. The apprecia- 

 tion of the book abroad is shown by the fact that the edition 

 which is now translated is the third edition since its original 

 publication in 1S66, the third edition of the first part of the text- 

 book being demanded before the second part was ready for publi- 

 cation. The valuable scientific researches of Hertwig are very 

 well known by all naturalists, and his name alone is sufficient to 

 indicate the reliability of the work in hand. 



The title, " A Text-Book of Embryology of Man and Mam- 

 mals," does not adequately express the scope of the book, for 

 while it is in details largely confined to the study of mammals, 

 there is so much of general embryology within its covers as to 

 give it a value as a general text-book of vertebi'ate embryology. 

 As such a text-book it is of the greatest value to a student, and 

 it is safe to say that at the present time there is no text-book so 

 well designed to give the student a general knowledge of verte- 

 brate embryology as the present one. 



The subjects treated comprise all matters of importance con- 

 nected with invertebrate embryology. They are treated in a 

 masterly style, and the facts and discussions are in all cases 

 brought up to date. In the chapters on the sexual products and 

 their fertilization may be found a summary of the essential facts 

 of our present knowledge upon this important subject. The 

 chapter on cleavage discusses the general matter of the segmenta- 

 tion of eggs, giving the various types of such segmentation, their 

 relations to each other and defining the terms used in descrip- 

 tions in various text-books. The chapter on the gastrula is espe- 

 cially valuable, for it gives in a clear, logical, but concise man- 

 ner, illustrated b.v valuable and intelligible drawings, our present 

 ideas as to the application of the gastrula theory to the embry- 

 ology of vertebrates Ic is a subject which is always puzzling to 

 the student of embryology to understand the gastrulation of the 

 vertebrate egg, and Professor Hertwig has done very much 

 toward making this difficult subject intelligible. Not the least 

 valuable part of this section is an outline history of the gastrula 

 theory, tracing our knowledge of embryology of the germ layers 

 from its infancy to the present time. The gastrula theory is 

 accepted by Professor Hertwig in its fullest sense. The chapter 

 on the formation of the body cavity gives Professor Hertwig 

 an opportunity of explaining clearly his "coelomthorie" 

 which he does in a clear style, and the significance of which 

 he makes plain by its historical consideration. In addition 

 to the above, there are considered in the first part of 

 the work the segmentation of the vertebrate embryo, the origin 

 of connective tissues, the method of formation of the external 

 form of the vertebrate body and a study of the foetal membranes 

 of reptiles, birds, mammals, and man. In all of these sections 

 the aim of Professor Hertwig is not only to give facts but to give 

 a logical connective account of the significance of the facts and a 

 logical understanding of the various phases in the development 

 of the vertebrate body, and he has greatly added to the value of 



