204 



NATURE 



[Appii. 



H)i r 



buddinj;^ to another category. The writers, in fact, 

 suggest that the phenomena are not coordinate, and 

 that there would have been no diOlculty had not 

 "prospective significance" been confounded with 

 " prospective potentiality." That is, it is the peculiarity 

 of a bud to contain sets of cells which have j^reater 

 capacities than tlie embryonic layer from which they 

 were derived in the other manner of development. 

 .And yet, when it becomes necessary, to find some 

 general expression for the different modes of endo- 

 derm formation in Ccelenterates, to deduce them all 

 from some common origin, the "prospective signifi- 

 cance " is enlai^ed until it is big enough to include 

 as much " potentiality " as may be required ! 



The truth is that the anomalies are of the same 

 order in both kinds of reproduction. In both the 

 germ-layers have greater potentialities than they 

 normally display, and no theory of them can ever be 

 satisfactory that does not offer a general explanation 

 of their origin and differentiation, in the develop- 

 ment of the ovum, in budding, and in regeneration. 



To the phenomena of the last two kinds the test 

 of experiment has, as yet, scarcely been applied, but 

 we do fortunately know what the internal factors are 

 on which the differentiation of these first-formed em- 

 bryonic organs in the ovum depends. For experiment 

 has shown us that there are in the cytoplasm of the 

 unsegmentcd egg-cell certain substances — at least 

 certain regions — the removal of which entails the 

 absence in later development of some particular 

 embryonic or larval structure. The position of these 

 substances in the ovum need not be that in which 

 the corresponding organ eventually appears (the 

 apical sense organ of Denialitim depends on some- 

 thing present in the polar lobe of the egg), and the 

 manner in which this heterogeneous cytoplasm is cut 

 up into cells during cleavage is largely irrelevant, 

 the cleavage pattern being alterable, and, further, 

 determined by other, distinct, causes. Hence, though 

 normally these organ-forming stuffs pass into definite 

 cells, though in related forms the cleavage pattern is 

 alike, but not identical, though in related forms the 

 arrangement of the stuffs and the differentiation of 

 the organs is alike but not identical, nevertheless 

 variations in the cleavage unaccompanied by corre- 

 sponding variations in the cytoplasmic structure (or the 

 converse), necessarily lead to the production, in related 

 forms, of the same organ from a cell which has in 

 cleavage a distinct origin. The illustration applies 

 primarily to " spiral " cleavages— the nephridia of 

 Leeches comes from 4^, of Annelids from 2d, the 

 pericardium of some MoUusca from ectoderm, of other 

 MoUusca and of Annelids from mesoderm (4^), and 

 so on — but, mutatis mutandis, may be easily extended 

 to other cases. 



In truth, the substances out of which genuinelv 

 homologous, that is, phylogenetically homogeneous 

 organs are developed, must be themselvey 

 homologous. They exist in the egg antecedent to sedi- 

 mentation and gastrulation, and cannot be created 

 by those processes, in which therefore we look in 

 vain for any absolute criterion of homology. 



What experiment has done for the developing ovum 

 NO. 2163, VOL. 86] 



it will, we hope, before long accomplish aUu for 

 bud and the regenerating organism. Then, but 

 until then, shall we know what the internal factor^ 

 differentiation are in these cases also, and shall 

 able perhaps to show that the primary— cventualK 

 — the phenomena of their "increase of structure" 

 determined by the .same kind of material (ultimn- 

 physical and chemical constitution), as that 01 

 they are dependent in sexual reproduction. 



l!l'. 



WEBSTER'S SEW ISTERy M I()\ ] [. 

 DICriONARY. 

 Webster's New International Dictio 

 Ush Language. Based on the luu rutin, 'tuu uic- 

 tionary of 1890 and 1900. A'ou' completely revisedi 

 in all Departments, including also a Gazetteer and, 

 other Appendices. Edited by Dr. W. T. Harri»j 

 and F. S. .Allen. Pp. lxxx + 2620. (London: G. 

 Bell and Sons, Ltd.; .Springfield, Mass. I'.S. 

 G. and C. Merriam Company, niii 

 2/. 135. 6d. net. 



THE origin of " Webster " dates from ., 

 period in the history of works of reference, 

 second half of the eighteenth century. Noah Web- 

 ster, a teacher in the United States, entered upon 

 his earliest work of compilation about the same time 

 that "a society of gentlemen in Scotland" were pro- 

 ducing the first edition of the Encyclopaedia Britan- 

 nica in Edinburgh. His spelling book appeared in 

 1783 ; it doubtless contained the germ of his larger 

 idea, though this was not developed for many years 

 — the first edition of his dictionary only appeared in 

 1828. Apart from re-issues and supplements (and 

 also, to judge from a warning in the prospectus, 

 pirated editions), there have been two great revisions 

 of the original work before the present one, namely, 

 those of 1864 and 1890. Both in the method of pre- 

 senting facts and in mechanical construction the 

 " new " revision introduces changes so great as to 

 justify the use of the epithet in every sense, and 

 some of these changes are of much importance and 

 interest to all who have been led by frequent use 

 to formulate views on the right arrangement of works 

 of reference. 



In the first place, "Webster" is an "encyclopaedic" 

 dictionary, and in the present edition that quality 

 has been not only sustained but brought into greater 

 prominence. At one period in the history of the 

 making of works of reference, strong criticism was 

 directed against the encyclopaedic type of dictionary, 

 and on obvious grounds. It was, held to be the 

 function of a dictionary exclusively to state and 

 account for, historically and philologically, the origin 

 and meaning of each word, to attempt no disquisi- 

 tion as to its connotation, and to avoid any articu- 

 lated arrangement of historical, scientific, or other 

 information dependent upon any word as a "head- 

 ing." This latter function was left to the encyclo- 

 paidia exclusively. Proper names and place-names 

 were ruled out on the same grounds. On the other 

 hand, the encyclopaedia did not trench upon the philo- 

 logical functions of t^" dictionary, nor even, to any 



