266 



NA TURE 



[January 19, 1905 



been having our doubts about the homology of the 

 germ-layers and the like ; morphological concepts are 

 every day becoming more kinetic, less static. The 

 only question is how far we can go with the little that 

 we know of physiological morphology. In so far as 

 Garbowski has increased the data his memoir is very 

 welcome. 



(3) Dr. Em. RAdl has made many experiments on 

 the phototropism of animals, that is to say, on the 

 manner in which they orientate themselves in relation 

 to light stimuli. Pliototropic phenomena have been 

 most studied in plants, but there is already much 

 literature relating to their occurrence among animals, 

 and the author begins with a historical survey. He 

 goes on to the reactions of animals on a revolving turn- 

 table, the compensatory head-movements of insects, 

 nystagmus in insects, and phototropic orientation m 

 insects with one eye blackened. 



After showing that phototropic orientation or move- 

 ment occurs widely among animals, e.g. in Coelentera, 

 echinoderms, planarians, annelids, arthropods, and 

 molluscs, and that it may be exhibited in eyeless forms, 

 Rddl discusses various phenomena which cannot be 

 set down as simply phototropic. Thus it cannot be 

 safely said that the movement of pigment in the eye 

 or in the skin is phototropic. and there are many de- | 

 tails in the behaviour of butterflies and dragon-flies in j 

 relation to light and shade which seem to be more 

 than phototropic. A simple reflex may become com- 

 plicated by the association of accessory reflexes. In 

 unnatural conditions the established phototropic reflex 

 may lead the animal astray, as when the moth, circling 

 nearer and nearer, finally finds its death in the candle 



an interesting and much discussed subject to which 



Rddl devotes some attention. 



Sedentary animals, like plants, orientate themselves 

 to the direction of the light; freely moving animals 

 move into the direction of the light. The author dis- 

 cusses the question whether these two kinds of re- 

 sponse are merely different aspects of phototropism, 

 and comes to the conclusion that the two are not 

 directly dependent on one another. He also regards 

 the difference between positive and negative photo- 

 tropism as a secondary matter ; in both there is orienta- 

 tion to the direction of light, but the locomotor muscles 

 are differently stimulated. 



In the more general part of his book, Radl discusses 

 the relations between phototropism and other tropisms 

 — or the more legitimate of these — geo-, stereo-, rheo-, 

 galvano-, chemo-, and thermo-tropisms. There is a 

 chapter, all too short, on the ethological importance 

 of phototropism. The author is clear that organisms 

 are systems of adaptations and that phototropism is a 

 physiological adaptation, but he looks askance at 

 teleological phraseology, and does not follow up the 

 subject. The book closes with a discussion of the 

 general theory of orientation ; this must be based on 

 study of tropisms; there is no " Orientierung iiber- 

 haupt," but the organism seeks for a state of 

 equilibrium in relation to various external stimuli — an 

 equilibrium which consists not merely in the position 

 of the body, but in its functioning. 

 NO. 1838, VOL. 71] 



Dr. Rddl is cautious in stating his own theory of 

 phototropism ; he restricts himself to the following 

 propositions : — 



(i) Phototropic orientation means the rajjacity of 

 assuming a definite position of the axis of ihc body in 

 the field of light. 



(j) .A phototropically orientated organism is in a state 

 of physiological equilibrium in relation to the light. 



(3) The orientation can only be brought about by tht- 

 operation of paired or coupled forces, which are partly 

 external, partly internal. 



(4) In the orientations or tropisms of organisms there 

 is always at least one internal force operative, and 

 this is usually muscular. 



The conclusions strike one as disappointing, for they 

 seem to be practically summed up in the conception of 

 " physiological equilibrium "; those who are prepared 

 to advance other theories will find this book of great 

 service. It summarises the subject, describes many 

 new experiments, and criticises many untenable 

 positions. 



(4) .\bout twenty years ago we were familiar w'ith a 

 little book, " Outlines of Zoology," by Graber, which 

 had a wide use if not popularity in Gymnasien. Its 

 features were brevity, accuracy, lucidity, and compre- 

 hensiveness. We suppose, in the absence of any pre- 

 fatory note, that the volume before us is our old 

 acquaintance in a glorified edition, in which Dr. Latzel 

 has preserved the characteristics of the original. The 

 book begins with a short introduction on metabolism,^ 

 the cell, and protoplasm — which must be difficult 

 pabulum for even " hohere Lehranstalten " ; it pro- 

 ceeds to the structure and functions of the human body^ 

 and thence to a survey of the whole animal kingdom 

 from mammals to the Protozoa. .As a systematic 

 summary to be associated with more vital studies in 

 natural history the book is admirable ; it is clear, 

 direct, accurate, and most copiously illustrated. It is 

 so ambitiously all-inclusive that we are almost startk^d 

 to find no mention of Balanoglossus, Peripatus, or the 

 okapi ; but these will doubtless find their place in the 

 next edition. A book of this sort, tightly packed with 

 information, without, in many cases, even the padding 

 of verbs to the sentences, must be judged by its inten- 

 tion. If that be, as we charitably suppose, to serve 

 as a terse index rerum or synopsis, associated with 

 practical work and open-air studies, it deserves to be 

 encouraged. But if it is meant as a book to be " got 

 up " — and there are unpleasant suggestions of the 

 cram-book about it — then it is emphatically not in the 

 line of progress. It stands in direct antithesis to the 

 natural history text-books for high schools which find 

 favour in .\merica and are securing their place in this 

 country. There is almost no suggestion of the evolu- 

 tion or affinities of the great types ; there is almost no 

 hint of initiation into scientific methods of observation 

 and reasoning; and there is very little open-air. It 

 seems to us more like a revisal-book for a student goini: 

 up for his first professional examination in medicini 

 or natural science than a book for schools. At the sanir 

 time, it is a very effective book of its sort; the illus- 

 trations are admirable, and the coloured plates are as 

 fascinating as the text is dry. J. .\. T. 



