Sept. 20, 1877] 



NATURE 



437 



from the middle of a star-like dichotomously-branched 

 mycelium, which radiates in a single plane. The zoo- 

 sporangia are separated from the mycelia by a transverse 

 wall. The zoospores are developed in small numbers, 

 and escape by a lateral opening. 



I. O. inncronatiim, nov. sp. In the empty skin of a 

 gnat-larva. 



III. Rhizidium, A. Br. 



I. R. mycophilum, A. Br., is fully described and figured, 

 and the resting-spores traced through their long period of 

 repose. 



IV. Cladochytrium, nov. gen., Now. The zoospo- 

 rangia are either developed as intercalar swellings of the 

 one-celled mycelium in the tissue of the host-plant, and 

 separated by transverse walls, or they are terminal at the 

 end of single mycelium threads. The zoosporangia dehisce 

 either by the opening of a long neck, or by a lid. 

 Secondary zoosporangia are developed either in rows or 

 in the interior of old empty zoosporangia. 



1. C. ttiiuc, nov. sp., in the tissues of Acorus calamus, 

 Iris pscudacorus, and Glyceria speciabilis. Closely related 

 to Protomyccs 7iicnyanthis, De Bary found in the leaves 

 and petioles of Mciiyaiithes trifoliata. 



2. C. elegaiis, nov. sp., in the gelatinous substance of 

 Chatophora clcgaits. 



The last paper is by Prof. Cohn himself — " Remarks 

 on the Organisation of Certain Swarm-Cells." It is chiefly 

 devoted to an account of Conimn ictras, A. Br., and cer- 

 tain subjects suggested by the examination of that plant, 

 such as the nature of the " amylum kern," or starch 

 nucleus, the inner organisation of swarm-cells, the cavities 

 and contractile vacuoles in such cells, and the com- 

 parison of swarm-cells with one-celled animals. The 

 whole number is one of great interest and will well repay 

 perusal. W. R. McNab 



OUR BOOK SHELF 



Physios^aphy and Physical Gecoraphy. By the Rev. 

 Alex. Mackay. (Blackwood and Sons.) 



In his preface the author draws attention " to the 

 peculiar character of the present work," and quotes by 

 way of explanation two paragraphs from the Directory 

 of the Science and Art Department. He remarks that 

 " the student will at once peiceive that the author has 

 discussed all the subjects embraced in the new syllabus " 

 of the department. The spirit of this discussion and 

 "the peculiar character of the work" will be best appre- 

 ciated from a few extracts. 



"The combined result of various experiments gives to the 

 earth a density of 5 '66 times that of water. But more reli- 

 ance should be placed on the number indicated by the Great 

 Pyramid, which in this as in so many other great cosmical 

 data, has anticipated modern science by more than 4,000 

 years." "The sacred volume declares that in the days of 

 Noah the whole world was inundated by a flood, which 

 covered the highest mountains, and that, with the exception 

 of one family, the entire human race was destroyed. A 

 change in the inclination of the earth's axis would certainly 

 produce such a catastrophe — a catastrophe which was 

 accompanied with direful results to all future generations ; 

 the alternations of heat and cold became so rapid as to 

 affect the longevity of man, which has from that date 

 gradually shortened from nearly a thousand years to 

 three-score years and ten." "Why the planets move in 

 elUptical orbits " is the title of a paragraph, which, con- 

 taining no reference to nor explanation of the ellipticity 

 of the planetary orbits, is embellished with a diagram to 

 show why the orbits are circular. " Mountain-chains of 

 the same geological formation are believed to be of the 

 same antiquity ; and, however widely separate, are 



parallel to one another." " The slow increase in the salt- 

 ness of the ocean may account for the otherwise inexpli- 

 cable fact that frequently since the ocean became 

 inhabited, its varied population became wholly or almost 

 wholly extinguished." " The antiquity of the human 

 species as indicated by geological evidence, no doubt 

 conflicts with the chronology of Usher, founded on our 

 modern Hebrew text. In the matter of antediluvian 

 chronology, however, the Hebrew tej.t has, in all proba- 

 bility, been tampered with, as we have shown at large in 

 a separate work (' Facts and Dates,' p. 62-69). The 

 Septuagint translation — a translation sanctioned by our 

 Lord and his Apostles — assigns to our race an antiquity 

 of nearly 1,500 years more than Usher does. Science is 

 giving its emphatic verdict, in this particular, in favour of 

 the Septuagint ; and though the extended chronology 

 may fail in meeting all the difficulties of the case, it will 

 certainly meet many of them . . . Geologists are too apt 

 to toy with millions of years as if they were playthings, 

 and to show no regard to moderation or common sense. 

 Science has not hitherto been able to determine the actual 

 antiquity of the planet, and probably never will." 



T/ic Book of Algebra. By A. T. Fisher, B.A. (London : 

 Stewart's Local Examination Series, 1877.) 



Mr. Fisher has aimed at writing a short work on algebra 

 for students who have no intention of reading high 

 mathematics. He has done his task well, and the result 

 is a compact and carefully put together little book. The 

 limit he has set himself is to enable a reader to under- 

 stand all that is required as preliminary to the solution 

 of higher simultaneous equations ; hence we have nothing 

 on the Progressions, Notation, Permutations, &c. On a 

 perusal of the work we have been especially struck with 

 the care taken by the author to bring out a book bur- 

 dened as httle as possible with mistakes. For three- 

 fourths of the book he has been assisted by the printers, 

 but in the chapters on surds, indices, and higher equations 

 we have noticed a plentiful crop of typographical errors. 

 Most of these are, however, easily corrected. There is 

 an unfortunate mistake of + for X twice on p. 47 ; of 

 - for -~- in Ex. 14, p. 52. 



Some readers would require a larger number of ex- 

 amples ; those that are given are, on the whole, verj' well 

 chosen, and there are some useful problems neatly solved. 

 It is possibly an objection, certainly in the elementary 

 parts, that the answers immediately follow the questions. 

 The book is neatly, and for the most part carefully, 

 printed. 



Bulletin of the United States Geological and Geographical 

 Survey of the Territories. Vol. iii. No. 2. (Wash- 

 ington, 1877.) 

 The second number of the above Bulletin contains three 

 important entomological articles from the pens of Messrs. 

 Osten Sacken, Uhler, and Thorell. 



The first memoir, from the pen of that distinguished 

 Dipterist, Baron C. R. Osten Sacken, bears the modest 

 title of " Descriptions of New Genera and Species of 

 Diptera from the Region West of the Mississippi, and 

 especially from California," but he who takes up the 

 paper expecting to find nothing but bare descriptions 

 will be agreeably surprised to find it interspersed with 

 analytical tables of the Diptera of the United States, 

 with diagnoses and critical notes on many species already 

 known, with remarks on their geographical distribution, 

 synonymy, and in fact anything that could in any way 

 contribute towards rendering this order of insects clear of 

 comprehension or attractive to the student. 



The second article, by Prof. P. R. Uhler, is a report on 

 the insects collected by himself during the exploration of 

 1875, including monographs of the hemipterous families 

 Cydnidce and Saldce, and an account of the hemiptera 

 collected by Dr. A, S. Packard, jun. The monograph of 



