Jan, 25, 1877] 



NATURE 



2Jl 



to about twenty-two per cent, of that which is evolved ; 

 whereas in the case of magnesium, under circumstances 

 as similar as possible, it is only about eight per cent. 

 This, indeed, is but a portion of the broad problem of the 

 connection between the conditions of a chemical change 

 and its amount, one side of which, as Dr. Armstrong 

 shows us, has already been attacked by Messrs. Harcourt 

 and Esson. We may add, in this connection, that it 

 would have conduced to clearness if, in the concise 

 account of the work of these chemists, the term 

 " thiosulphate " had been substituted for that of " hypo- 

 sulphite," since we have the existence of Schiitzenberger's 

 acid duly stated a i&'w pages further on, and it, in accord- 

 ance with Henry Watts's suggestion, is called hyposul- 

 phurous acid. 



Of the remaining portion of the article, namely, that 

 on organic chemistry, we have but little space to speak. 

 In one respect Mr. Meldola has had the most difficult 

 share of the work, for it is no light task to be obliged to 

 concentrate the essence of modern organic chemistry 

 within less than forty pages. The general arrangement 

 of this section bears considerable resemblance to that of 

 Prof. Schorlemmer's excellent Manual of the Carbon Com- 

 pounds, and although it, of necessity, cannot be attrac- 

 tive to the general reader, we can congratulate Mr. 

 Meldola on having produced a compilation which will be 

 highly serviceable to chemists. T. E. T. 



PACKARD'S LIFE-HISTORIES OF ANIMALS 



Life- Histories of Aiiitnals, including Man ; or, Out lines 

 of Cojnparative Embryology. By A. S. Packard, jun. 

 (New York : Holt and Co.) 



IN the rapidly-shifting condition of our knowledge of 

 the development of all kinds of animals, it is a most 

 difficult thing to produce a satisfactory treatise on Com- 

 parative Embryology. None the less such a work is 

 much needed by our university students, and the little 

 book which Dr. Packard has put together may be recom- 

 mended to them as containing a great deal of the latest 

 information on the subject, well illustrated by diagrams 

 derived from a number of widely-scattered German, 

 French, English, and American periodicals. 



At first sight Dr. Packard's book appears considerably 

 better than it really is. The student needs to be cau- 

 tioned in using it, since it combines with much that is 

 excellent a surprising amount of inaccuracy, and is sadly 

 deficient in critical power. Dr. Packard is a student of 

 German zoological journals, and is too ready to attach a 

 large measure of importance to German work because it 

 is German. Moreover, though he has himself engaged 

 in researches on the embryology ot the King Crab and of 

 Insects, he has clearly not worked over a wide field in the 

 subject, and consequently is not able to bring a trained 

 experience to bear on the discrimination of the sound 

 and the unsound observations and speculations of recent 

 writers. 



Amongst the good points of the book (to take some of 

 these to begin with) we have a figure supplied by Dr. 

 Bessels of his Protobathybius Robesonii ; the account and 

 figures of various Monads from James Clark, Dallinger, 

 and Drysdale ; the text and figures relating to the 

 Echinoderms ; Lacaze Duthier's figures of developing 



Dentaliuin : figures relating to the development of 

 Arthropods from the works of Bobretzky, Kowalewsky, 

 andGanin; Morse's figures of developing Terebratulina ; 

 Agassiz's Tornaria and Balanoglossus ; Wyman's embry- 

 onic skates ; whilst good figures of larval Ascidians are 

 also given. 



Whilst insisting on the service which the book will 

 render to the young student, we shall now point to some 

 of its shortcomings. In the first place it is somewhat 

 misleading to call attention in the title of the book to the 

 two pages which are devoted to man. The Vertebrata 

 altogether, are not treated with the same proportion of 

 attention, relatively to our knowledge of them, as are the 

 lower groups of animals. 



It may be pointed out that whilst giving a large 

 number of very useful citations of recent embryological 

 works, Dr. Packard is not uniformly careful to ascribe 

 the use of the terms and genealogical hypotheses which 

 he employs to their rightful authors. In his chap- 

 ter on the life-history of the MoUusca, he makes use 

 of the terms Trochosphere and Veliger which I intro- 

 duced into embryological nomenclature in my paper 

 on the Development of the Pond Snail {Quart. Jotirn. 

 Micros. Science, 1874), which he cites at the end of the 

 chapter ; he does not, however, ascribe either the terms 

 or the views connected with them to their author. I 

 am induced to mention this omission specially, since 

 Prof. Semper of Wiirzburg, in his last publication — a 

 heavy octavo discussing the relationship between Verte- 

 brates and Annelids — has made a leading feature of the 

 Trochosphere, appropriating the name as applied by me 

 and the doctrine connected with it, without the slightest 

 acknowledgment. The impropriety of Semper's proceed- 

 ing is the greater since he makes no mere passing allusion 

 to the Trochosphere, but puts forward a " Trochosphere- 

 theory " which is intended to eclipse the " Gastrula- 

 theory " of Haeckel. 



A few points amongst those which we have noted as 

 blemishes may be conveniently cited in order of pages. 



Page 3. — We read " Bathybius was first discovered by 

 Prof. Wyville Thomson in 1869, in dredging at a depth of 

 2,435 fathoms at the mouth of the Bay of Biscay." It 

 was not, but was described and named by Huxley in 

 1868. Thomson appears to have seen it in 1869, in a 

 living state under the microscope, to judge from his 

 description quoted by Packard. Presumably this was 

 not the sulphate of lime with which Bathybius has since 

 been identified by the same authority. 



Pages 24 and 25. — Urella should be Uvella. 



Page 54. — " We have by tearing apart a species of 

 Sycandra (or Sycon) perhaps S. ciliata, which grows on 

 a Ptilota, found the planula much as figured by Haeckel, 

 Metschnikoff, and Carter, and anyone can with patience 

 and care observe the life-history of the marine sponges." It 

 would have been more satisfactory if Dr. Packard had 

 told us whether the planula^ he saw were like the figures 

 of Haeckel or those of Metschnikoff ; they certainly could 

 not have been like both. It is a mistake to dismiss one 

 of the most difficult problems which is now baffling 

 embryologists with the assurance that " anyone can with 

 patience and care " solve it. 



Page 96. — " Sprat " for young oysters should be "spat." 

 Salensky's observation on the young oyster, and his erro- 



