March 24, 1892] 



NATURE 



483 



development of the species ; or, to put it more simply, 

 animals in their development climb up their own genea- 

 logical trees. This is now generally accepted by embryo- 

 logists, but it has not always been so, and Haeckel 

 reminds us, with justice, that he was one of the first to 

 realize and teach the doctrine. 



Prof. Haeckel has much to say on other points of 

 theoretical interest. He protests strongly against Weis- 

 mann's views with regard to heredity, pointing out that 

 the very existence of germ-plasmi is as yet a mere assump- 

 tion, and maintaining that acquired characters maybe and 

 are actually transmitted. He objects equally strongly to 

 the views as to the widespread occurrence of degenera- 

 tion, which were first put forward by Dr. Dohrn ; and on 

 the much-debated question of the origin of Vertebrates 

 he sides with those who fully accept the evidence afforded 

 by the anatomy and development of Amphioxus ; he 

 admits the Vertebrate affinities of Balanoglpssus, and 

 looks for the ancestors of Vertebrates among the un- 

 segmented Turbellarian worms. As a controversialist 

 Prof. Haeckel is impressive rather than convincing. He 

 hits hard and with effect, but prefers to counter rather 

 than to parry the blows of his opponent. It is impos- 

 sible to pass over without protest the terms in which he 

 writes— it must be admitted under provocation — of tlie 

 opinions and work of other investigators. 



Prof. Kaeckel's fondness for genealogical trees, and 

 his facility in constructing them, are well known and 

 have been much criticized, perhaps a little unfairly. 

 Acceptance of the doctrine of evolution involves the 

 recognition of a blood-relationship, near or remote, 

 between any one animal and any other ; and the only 

 true classification is one which places this fact in the 

 forefront, and adopts it as the basis on which the 

 scheme is to rest. Genealogical tables undoubtedly 

 stimulate inquiry, and so long as it is realized that 

 they are necessarily in great part tentative or pro- 

 visional, they probably will do more good than harm. 

 It would be easy to take exception to many points in 

 Prof. Haeckel's numerous and elaborate pedigrees, but 

 it will be generally admitted that they are instructive, 

 and often extremely suggestive, even though the con- 

 clusions may not meet with general acceptance. 



The least satisfactory part of the book is that which 

 deals with human embryology. No attempt whatever is 

 made to explain the earlier stages of development ; 

 the special difficulties of the problem are absolutely 

 ignored ; the human gastrula is spoken of in a confident 

 way, as though such a stage really existed ; and the 

 accounts of the development of the several organs and 

 systems are too often taken from other animals. A 

 student who relied on Prof. Haeckel's descriptions would 

 obtain an entirely erroneous idea of the actual course of 

 development of the human embryo. 



Owing to the difficulty of obtaining material in proper 

 condition for microscopical examination, our acquaintance 

 with human embryology long remained imperfect ; and 

 the descriptions in text- books were largely based on our 

 knowledge of other Vertebrates, and illustrated by figures 

 from embryos of dogs, pigs, rabbits, or even chicken 

 and dogfish. The time for all this is now past. During 

 the last ten years our knowledge has advanced wonder- 

 fully ; and although the earliest stages are still unknown, 

 NO. I 169, VOL. 45] 



it is not too much to say that our knowledge of the deve- 

 lopment of the human embryo, from a stage corresponding 

 to a chick embryo at the commencement of the second 

 day onwards, is as satisfactory, as complete, and as well 

 illustrated as that of any other mammal. 



For this great advance we are indebted almost entirely 

 to the labours of German embryologists, and notably to 

 the splendid work of Prof. His. Prof. Haeckel has in 

 his volume many hard things to say of Prof. His, but is 

 indebted to him for the only really good figures of 

 human embryos which he gives, and would have mate- 

 rially improved his book had he studied more carefully 

 the admirable descriptions of the Leipzig Professor. It 

 is a matter for great regret that a book of 900 pages, 

 having for its title, " Anthropogenie, oder Entwickelungs- 

 geschichte des Menschen," should be allowed to appear 

 in which the account of the actual development of the 

 human embrvo is so inadequate or even erroneous. 



A. M. M. 



OUR BOOK SHELF. 



Philosophical Notes on Botanical Subjects. By E. 



Bonaviii, M.D. With 160 Illustrations. 368 pages. 



(London : Eyre and Spottiswoode, 1892.) 

 Dr. Bonavia's philosophy is concerned with the evolu- 

 tion of vegetable organisms, and the gist of it is that all 

 land-plants have descended from sea-weeds. He sees 

 modifications and traces developments not obvious to 

 ordinary observers, and he is prepared for derisive criti- 

 cism. To quote from his preface : — " The fact is that, in 

 this stage of existence, certain thoughts are often a great 

 worry. (Jne often cannot get rid of them. They turn up 

 by day, they turn up by night, they turn up in the morn- 

 ing, and they haunt one at all times, and the only remedy 

 for mitigating this worry of civilization is to commit them 

 to paper. This done, there are several ways of disposing 

 of your written thoughts. You can burn the papers they 

 are written upon or otherwise destroy them, or you can 

 leave them in a drawer as a legacy to your lieirs ! If by 

 neither of these processes can you entirely Ljive yourself 

 repose, then the most effective way of ridding yourself of 

 the worry of such thoughts is to have them published (if 

 any publisher will perform this kind office), and to see 

 them adversely criticized if anyone will even take so 

 much trouble." 



As the book before us testifies. Dr. Bonavia's worry 

 reached the acute stage, and he is so far relieved as to 

 have found a publisher ; but we do not propose to gratify 

 him by adverse criticism. We prefer giving one short 

 extract from his sixteen "general conclusions" :— 



" Fifteenth : — The fig is obviously a further develop- 

 ment of a conceptacle of a Fucus or other sea-weed. 

 And there is every reason to believe that the oil-glands 

 of the bark, leaves, and peel of the Citrus, and similar 

 glands in other plants, are mere remnants of sea-weed 

 conceptacles— that is, persistent features turned to other 

 uses." W. B. H. 



The Zoological Record for 1890. Edited by Frank E. 



Beddard. (London: Gurney and Jackson, 1892.) 

 This is the twenty-seventh volume of the Record of 

 Zoological Literature, and it has been prepared on the 

 same plan as the volume published last year. First of 

 all there is a list of works on general subjects, by J. A. 

 Thomson. Then come the titles of writings on the fol- 

 lowing :— Mammalia, by R. Lydekker ; Aves, by R. 

 Bowdler Sharpe ; Reptilia, Batrachia, and Pisces, by 

 G. A. Boulenger ; Tunicata, by W. A. Herdnian ; Mol- 

 lusca, Brachiopoda, and Polyzoa, by P. C. Mitchell ; 



