The three closing chapters dealing with Copernicus, Tycho, and Kepler are naturally those which command our special interest. They contain far more than mere statements of the works of these great heroes of astronomical science. They define clearly the specific rôle played by each of these actors in the revolution of scientific thought. In following the author through his analysis of "De revolutionibus," we realise not only the great mental power but also the heroism of the "quiet student at the shore of the Baltic," and we feel the importance of the moment when his work is ushered into the world with Osiander's apologetic introduction. We must agree with the author's endeavour to show how little Copernicus could have been influenced by Philolaus and the vague ideas of Aristarchus, whose anticipations detract nothing from the originality of his own thoughts. On the other hand, the exposition of the defects of the system is so lucid that it requires no intimate technical knowledge of astronomy to recognise the necessity of modification, which so immediately urged Tycho to the invention of his ingenious compromise between the geocentric and heliocentric conception. How far Tycho's all-important work as an observer has paved the way for the final recognition of the true system by Kepler is admirably shown in the last chapter, where the author opens before us the successive paths along which, through a labyrinth of errors and failures, the never tiring genius of Kepler was finally led to the "golden portal of truth." The long and weary road he had to go before he finally broke away from the time-sacred idea of circular motion and the Ptolemaic punctum aequans, and proved conclusively the elliptic character of the Martian orbit, is brought before us by an exhaustive analysis of his works, the study of which is so highly instructive, not only from the scientific, but also from the psychological point of view. The reproach, often levelled against the author of the "Mysterium Cosmographicum," of having filled his books with all sorts of mystic fancies, is, in Dr. Dreyer's opinion, founded on a misconception of Kepler's object in making his investigations. "There is the most intimate connection between his speculations and his great achievements; without the former we should never have had the latter."

We cannot attempt to enter upon the author's review of the opinions of science and church on the Copernican system during the time between Kepler and Newton, with which, on the whole, the student of history is familiar, though it is particularly interesting to hear on this matter the verdict of an historian who has derived his knowledge so directly and completely from an exhaustive study of the original prints and manuscripts.

It is difficult to emphasise sufficiently the specific merits of a work of this kind in a brief review. Doubtless not the least of its many meritorious features is the lucidity and conciseness of exposition. In its endeavour to grasp the essence of the cosmogonic ideas the mind is nowhere impeded by an unnecessary accumulation of cumbersome detail. At the same time the non-mathematical reader is sup

plied with sufficient technical information to secure his acquaintance with the principal geometry of the cosmic systems under discussion. This latter advantage is important in the case of a work which is clearly not written for a limited circulation among the small section of astronomical experts, but may justly claim to appeal to all who are interested in the history of the general development of scientific culture.

Vols.

PROF. EHLERS'S "FESTSCHRIFT." Zeitschrift für wissenschaftliche Zoologie. lxxxii. and lxxxiii. Festschrift zur Feier seines siebzigsten Geburtstages am 11 Nov. 1905, Herrn Geheimen Regierungsrat Prof. Ernst Ehlers. Band i., pp. iv+692; Band ii., pp. 741; and plates. (Leipzig: Engelmann, 1905.) 2 vols., price 51. whose honour THE distinguished zoologist in

these volumes are issued is widely known as an indefatigable worker and one of the most genial Ehlers has for many years edited the journal which of men. Together with the late von Kölliker, Prof. now celebrates his seventieth birthday. As a testimony of the inspiring character of his teaching and of the regard in which he is held this "Festschrift " gives abundant witness. With no less clearness it indicates the diverse activities of modern zoologists and the particular problems upon which they are engaged.

With such a varied content, the volumes are difficult to review. The systematic work, admirable as it is, and coordinating or expanding as it does our knowledge of annelids, starfish, and flat-worms, can only be mentioned; nor can we do more than indicate the purport of a few of the many anatomical and physiological papers.

The place of honour is appropriately given to von Kölliker's paper on the histogenesis of the verte. brate nervous system, the last contribution of the master of histology, whose amazing vitality at eighty-seven years enabled him to conduct research and to discuss difficulties of fact and interpretation with unabated zeal. The month in which this latest defence of the neuron-theory was published brought the tidings that von Kölliker had ceased from work. A long and exquisitely illustrated memoir by Vejdowsky gives a minute account of the structure and mode of origin of the annelidan vascular system. The nature of this system in the lower animals has been of late the goal of much research. Under the influence of the trophocal theory, as stated by Lang on the basis of Bergh's work upon annelids, the vascular system has come to be regarded generally as a mesodermic structure, its cavities as a schizocoel, and not, as had often been suggested, a blastocœlic structure. The results of Vejdowsky's work have led him to a very different conclusion. First he proves, what had often been denied, that annelids possess a vascular endothelium. He finds that this vasothelium" arises in the following way. Blood-vessels are intimately associated with the gut. Their cavities are at first simply a space between the outer ends of the gut-cells and their basal membrane. Into this space cells are budded off from the endo

44

derm. Some of these become differentiated into epithelio-muscle elements that constitute the vasothelium, and others into blood-cells. Thus the study of annelids leads Vejdowsky to conclude that their hæmocol is a hypoblastic structure sui generis, not comparable to that of arthropods or of molluscs, but rather to the cardiac vasothelium in vertebrates. Such a result emphasises that relation of vascular system to the alimentary tract which topography has insisted upon.

In his article on the morphology of the cestode body, Prof. Spengel stoutly supports the monozoic theory. He regards the Bothriocephalidæ as the most primitive tapeworms, and considers that in the highly modified Tæniidæ we have simply a coincidence of somatic and gonidial segmentation areas. Incidentally he suggests the comparison of the scolex with the hinder end of segmented worm, and emphasises the singular nature of the cestodes by pointing out their entire lack of true regenerative power.

The remaining anatomical papers deal with the modifications of clasping organs in arboreal mammals, with the head of collembolous and culicid insects, the nervous system of leeches, and certain abnormal gasteropods.

Of the embryological memoirs, the accurate and laborious research of Wierzejski on the cell-lineage of Physa will be welcomed as a topographical paper of the first rank. Prof. McIntosh contributes a well illustrated account of the life-history of the shanny, and then follow memoirs on the early development of the blind-worm, on the breeding habits of Rhinoderma and of the salamanders.

The physiological papers are of more general interest. Prof. Häcker continues his illuminating work on the skeleton of the Radiolaria by treating the Tripylaria from the same ecological standpoint which he adopted in his paper of last year. Häcker is the most active of a band of workers who are putting new life and new significance into the merely geometric descriptions of earlier students of these skeletal products. Dr. Rhumbler gives a further instalment of his work on the mechanics of streaming movement in Ambæ, and shows some interesting stream figures produced by dropping chloroform water upon shellac. He fully recognises the inward and autogenous control that dominates those displays in organisms that we cannot parallel in not-living matter, but he holds that in Amoeba the phenomena of movement and feeding are capable of mechanical explanation in terms of the aggregation theory which he has formulated elsewhere.

Dr. Jordan contributes an essay on the origin of species in Lepidoptera. His main thesis is to the effect that geographical subspecies, and no other variations, are the material out of which new species have been evolved. Much of the paper is summarised from his earlier work, and represents a line of research to which several naturalists are applying themselves. The work of Petersen on the Fritillaries in particular pursues the method employed by Dr. Jordan, but in a more comprehensive manner, and it

is to be hoped that these important results may be rendered more available to the student of evolution than they now are by a new mode of presentation, graphic, tabular, or other than textual description.

Lastly, the memoir of the Baroness von Linden on the influence of heat, cold, and gases upon the coloration of Vanessid butterflies constitutes a further instalment of the author's prolonged investigation. The general conclusion drawn from these experiments is that whatever lowers the rate of pupal metabolism increases amount of black imaginal pigment and diminishes the extent of red colour in the butterfly. F. W. GAMBLE.

THE BIRDS OF TUNISIA. The Birds of Tunisia. Being a history of the birds found in the Regency of Tunis. By J. I. S. Whitaker. 2 vols. Royal 8vo. Pp. xxxii +294 and xviii+410. Plates and maps. (London: R. H. Porter, 1905.) Price £3 3s. net.

THE

HE two handsome and beautifully illustrated volumes containing the history of the birds of the Regency of Tunis form a fitting crown to the years of work in the field, the museum, and the library which their author has devoted to the ornithology of this until recently little known country. They form too a valuable contribution to the avifauna of the western Mediterranean region; for although the present work purports to be merely a history of the birds noticed in Tunisia, and of their lives as observed in that country, the author has thought it advisable, when possible, to allude to the occurrence of the various species also in Algeria and Morocco, as likewise, in some cases, in Tripoli, and in the Mediterranean basin generally.

The articles on various warblers (especially the interesting remarks on their life-history), and other birds which are met with most commonly in that region, will be most welcome, even to those whose interests are restricted to the birds which figure on the British list. Tunisia, a long and somewhat narrow country, stretching from the Mediterranean back in the vagueness of the great desert, presents a great variety of natural features and climate; and the contrast between the well-watered, wooded and mountainous region north of the Atlas Mountains and the rainless, sandy and rocky desert country is very great. To these circumstances, and to the fact, pointed out by the author, that few countries are geographically so favourably situated as the Regency for the observation of the migration of birds, the wealth of the Tunisian avifauna is due. No less than 365 species and subspecies of birds are included in this work; and only about thirty-five of these have to be relegated to the roll of occasional and accidental visitors. Two beautiful photogravures give an excellent and most truthful idea of the character of the scenery and the traveller's mode of life in the south of the country; while other plates introduce the reader to some of those wonderful Roman ruins, so marvellously preserved in that dry, clear air, which so startle the inexperienced wanderer in the central parts of Tunisia.

52

Each species is fully described, and a careful account of its distribution in Tunis, with some observations on its range in the neighbouring Mediterranean countries, is followed by an interesting and graphic account of its nesting habits, song, and life-history generally.

The four natural divisions into which the Regency may be divided appear to have each certain species peculiar to it, or more abundant in it than in the other regions. Besides this, in the case of some resident species, such as the crested larks, for instance, different forms of the same species are to be found in the different regions, the variation of these forms being in some cases considerable, and not always limited to the coloration of the plumage alone, but occasionally extending to the structural parts of the birds. The crested larks, says the author, afford a striking example of the extent to which local variation may be carried by natural causes, and no country probably affords a better opportunity of observing and studying this subject than Tunisia. The author is naturally in favour of recognising subspecies, and the use of trinomials for them; and his remarks hereon and upon what constitutes a species and a subspecies may be read with great advantage.

Many noteworthy and peculiar birds may be studied in Tunisia, but probably the families of larks and chats are better represented than any other; of the former twenty-one and of the latter eleven species and subspecies are treated, and the fifteen beautifully executed coloured plates which adorn these sumptuous volumes are largely devoted to illustrating these two families. Tunis is indeed especially rich in larks; and years of study, a long series of specimens collected by himself, and an examination of the various types in museums and the literature of the subject, added moreover to his having had the advantage of observing the birds in life, have enabled the author to clear up many puzzling points respecting the specific and subspecific value of the numerous forms of larks. We have here a very clear and lucid exposition of the larks of the western Mediterranean basin; and especially of the crested larks (the most puzzling of them all), of which the author considers that there are two distinct groups, viz., one including the common crested lark of Europe, the other the smallbilled crested lark of Southern Spain, each with its allies.

un

The necessity for protective colouring is doubtedly great in a country like Southern Tunisia, where the scanty vegetation affords but little shelter to its feathered denizens. Hence it is that the plumage of most of the species resident in the desert and semidesert region harmonises with the sandy coloration of the soil. This is especially remarkable in the larks. But the author points out that although at first sight it may appear curious that the chats, more or less conexcept in a few instances, are

spicuously coloured, it will, however, be found that the conspicuously attired chats frequent, as a rule, rocky and broken ground full of dark clefts and fissures, where the rocks are sometimes black and in other cases of a glittering white, and in such situations a strongly marked plumage is really far less con

AMEBE AND THEIR ALLIES. British Fresh-water Rhizopoda. Vol. i. By James Cash, assisted by John Hopkinson. Pp. x+148+ xvi plates. (Ray Society, 1905.) Price 12s. 6d.

net.

THE

HE important discoveries that have recently been made on the morphology of Protozoa have revived the interest in British fresh-water amœbæ and their allies, and a monograph on the subject has been regarded for some time as a special need of the zoologist.

As a

Mr. James Cash has been known for some years as an ardent microscopist with a special knowledge of the forms and habits of the species of fresh-water rhizopoda in the north of England, and he has given us in this volume the benefit of his experience in this line of work, illustrated by many beautiful original drawings of the living organisms. work of reference for the names of species, and in so far as it suggests to the young amateur naturalist exercises for his amusement and instruction, it will be useful; but as references to important details of structure and reproduction are in general meagre, often misleading, and in many instances omitted altogether, it will not supply the need that is felt The description of the cell (p. 3) as "physiologically, a minute vesicle, or closed sac, the enveloping mem brane or cell-wall enclosing the protoplasmic substance in which the functional phenomena reside," appears to us singularly unfortunate in an introduction to the study of the Protozoa.

The description of the nucleus is very short, but long enough to contain considerable extracts from the work of Calkins, whose views the author adopts, but there is no reference to the chromidial network which the recent papers of Hertwig, Schaudinn, and others have shown plays such an important part in It is reproductive phenomena of many rhizopoda. disappointing to find no reference, either in the introduction or in the systematic part, to the evidence of a developmental cycle in the life-history of Amœba, based on the researches of Scheel and Calkins.

In the very brief account of the reproduction of Arcella, again, although Hertwig's important paper published in Kupffer's Festschrift is included in the list of references, the statements made are incomplete and misleading. Many other criticisms similar to these could be made, but the critic is disarmed by the confession in the preface that the author has not "investigated very closely the physiological problems associated with the life-history of these organisms." With this confession before them, it seems difficult to account for the action of the council of the Ray Society in undertaking the publication of this mono