September 1, 1905.] 



SCIENCE. 



267 



tion of the changes in progress is in gen- 

 eral too vagTie to admit of the formation 

 of profitable theories. 



We have seen that it is possible to trace 

 the solar system back to a primitive nebula 

 with some degree of confidence, and that 

 there is reason to believe that the stars in 

 general have originated in the same man- 

 ner. But such primitive nebulae stand in 

 as much need of explanation as their stellar 

 offspring. Thus, even if we grant the ex- 

 act truth of these theories, the advance 

 towards an explanation of the universe re- 

 mains miserably slight. Man is but a 

 microscopic being relatively to astronom- 

 ical space, and he lives on a puny planet 

 circling round a star of inferior rank. 

 Does it not, then, seem as futile to imagine 

 that he can discover the origin and tend- 

 ency of the universe as to expect a house- 

 fly to instruct us as to the theory of the 

 motions of the planets? And yet, so long 

 as he shall last, he will pursue his search, 

 and will no doubt discover many wonder- 

 ful things which are still hidden. We 

 may indeed be amazed at all that man has 

 been able to find out, but the immeasur- 

 able magnitude of the undiscovered will 

 throughout all time remain to humble his 

 pride. Our children's children will still 

 be gazing and marveling at the starry 

 heavens, but the riddle will never be read. 



G. H, Darwin. 



SCIENTIFIC BOOKS. 



Index Filicum, sive Enumeratio omnium 

 generum specierumque Filicum et Hydrop- 

 teridum ah anno 1753 ad annum 1905 des- 

 criptorum adjectis synonymis principalihus, 

 area geographica, etc. By Carl Christen- 

 SEN. Copenhagen, H. Hagerup. Fasc. I, 

 pp. 1-64, May 5, 1905 ; f asc. II, pp. 65-128, 

 July 1, 1905. Price 3s. 6d. per fascicle. 

 The present notice of the first -two fascicles 



of Herr Christensen's ' Index Filicum ' is 



oilered not so much in the nature of a review 

 as with the especial purpose of calling the 

 v/ork to the attention of botanists and librar- 

 ians, and of urging the desirability of imme- 

 diate and deserved support. For, as we have 

 been informed by the author, unless very defi- 

 nite encouraglnent is given at once in the 

 shape of additional subscriptions it will be im- 

 possible to bring the printing to a successful 

 conclusion. The manuscript is said to be 

 quite complete, comprising ten or twelve parts 

 in all, the result of years of patient, tedious 

 effort. How unfortunate the discontinuance 

 of publication would be is realized most by 

 those who have borne in some measure the 

 burden imposed by the lack of such a com- 

 pendium. 



The work when complete is to be under 

 three heads : (1) A systematic enumeration of 

 the genera of ferns, based mainly upon the 

 treatment of Engler and Prantl; (2) an 

 alphabetical arrangement of all valid specific 

 names and synonyms published from 1753 to 

 1905, with mention of names in use among 

 gardeners; (3) an alphabetical catalogue of 

 references to the principal systematic liter- 

 ature of ferns. Of these it is undoubtedly the 

 second which, under present conditions, will 

 prove of greatest service to botanists; yet the 

 first is assuredly a great desideratum, and the 

 last will be of unusual benefit to younger stu- 

 dents. 



The want of an index has been pressing. An 

 authoritative estimate upon the validity of 

 the exceedingly numerous species proposed in 

 the past is, of course, a prime consideration; 

 but it can not be denied that this is best deter- 

 mined, or at least maintained, in an extended 

 descriptive work that shall afford a general 

 view of related species. It is too much to 

 expect that in the present instance the treat- 

 ment of species will carry the weight of mono- 

 graphic authority. Nevertheless, there is 

 every indication that the author's estimate is 

 a fair one; and, at any rate, deviation from 

 this treatment will not detract materially from 

 the usefulness of the work. 



The main value of the volume will reside in 

 the strictly bibliographic phase; the chief re- 

 quirement being, in brief, that we may be able 



