September 8, 192 1] 



NATURE 



43 



gregates some 20-40 ft. below, remaining in position 

 until she gets under way and quits the spot. 



A diver hanging in the shoal has a clear space 

 some 6 ft. wide around him ; beyond this the water 

 is crammed with mackerel, the outline of the shoal 

 corresponding roughly with that of the ship above. 

 One sees that the fish are feeding on plankton, not 

 by steadily pumping the water through their gill- 

 filters, but snatching gulps from different directions, 

 turning their eves about and making little jumps here 

 and there. Evidently the depth they maintain, 

 slightly different from day to day, is that at which 

 their food is drifting ; but what is the mysterious 

 attraction that keeps roving fish fixed beneath a 

 stationary ship for hours together? 



A paper by BuUen in the Journal of the 

 Marine Biological Association for June, 1912, pro- 

 duces evidence (from examination of stomach contents 

 and aquarium observations) that mackerel when feed- 

 ing on plankton exercise selective powers, picking 

 out certain forms, such as Copepods, and rejecting 

 others, presumably by visual means. After observing 

 the shoals on many occasions while hanging sus- 

 pended in. their midst, I feel sure that it is the assist- 

 ance given by the black background of the ship to 

 visual selection that links the fish to her. 



Most objects floating in the open seas, jellyfish, 

 sharks, driftwood, or derelicts, when carefully ap- 

 proached, are found to be accompanied by fish satel- 

 lites. The attractive force is not necessarily the same 

 in everv case, but where (as in the case of the 

 mackerel under the salvage ship) the stomach contents 

 turn out to be selected plankton it is probably a 

 matter of illumination. 



It is likelv that each member of a shoal is benefited 

 bv the background afl'orded by the bodies of its im- 

 mediate neighbours, and, if so, a factor in the shoal- 

 ing habit comes to light. Going deeper, a use sug- 

 gests itself for the lateral light-producing organs of 

 some bathvpelagic fishes which are so placed that 

 thev can scarcelv assist the fishes' own vision. 



G. C. C. Damant. 



H.M. Salvage Vessel Racer, Lough Swilly. 



Co-operative Indexing of Periodical Literature. 



I AM much interested in the leading article in Nature 

 of June q entitled "Co-operative Indexing of Periodical 

 Literature," because the H. W. Wilson Company is 

 doing on a commercial basis what the publications 

 you mention are doing on what you call a "co-opera- 

 tive basis." This, leads to an inquiry as to when the 

 publication of an index or abstract is "co-operative." 

 Perhaps co-operation meant originally the donation 

 of indexing work on the part of individuals or 

 libraries. However, it appears that of the co-operative 

 publications mentioned none of the editorial work is 

 donated. The "Engineering Index" is now pub- 

 lished bv one of the great engineering societies, .and 

 its deficit paid bv that -society. The deficit of the 

 " Index Medicus " is met by the Carnegie Institution 

 of Washington. The deficit of the "Index to Legal 

 Periodicals," published by the H. W. Wilson Com- 

 panv, is made good out of the treasury of the Asso- 

 ciation of Law Libraries, and the deficit of the 

 ".Agricultural Index" is made good out of the 

 treasurv of the H. W. Wi'son Company. In the 

 case of all these publications subscriptions are 

 solicited, and the income is used to pay for editorial 

 work and expenses so far as it will go, the deficits 

 being met as stated. Is the publication of an 

 index less "co-operative" if the deficit is met by 

 an individual or a corporation than if it is met 

 bv an association or a foundation ? In other words, 

 should not a corporation engaged in an educational 



NO. 2706, VOL. 108] 



work be recognised as '• co-operating " with men of 

 science and scholars in the difi'usion of knowledge? 



Librarians say that indexes are more used in 

 libraries than abstracts and digests. This, of course, 

 does not imply that abstracts and digests are not 

 useful to scientific and professional people, but since 

 the chief support for abstracts, indexes, and digests 

 comes from libraries, should not the advice of 

 librarians be considered? A mere examination of the 

 physical condition of various indexes and abstracts in 

 libraries might be a fair indication of their compara- 

 tive usefulness, and prove to be a tevelation to those 

 who are paying some of the deficits. 



At one time the subject of agriculture was con- 

 sidered bv the Committee on the International Cata- 

 logue of Scientific Literature, and it was expected 

 that a volume covering this subject would some time 

 be published. The publishing of our " Agricultural 

 Index " gives opportunity to compare the value of a 

 diction rtry-catalogue published on the " cumulative 

 plan " monthh', annually, and triennially with a classified 

 catalogue published only (and tardily) as an annual. 

 Would it not be interesting to make inquiries among 

 those who use such reference tools most in order to 

 determine what method is most efficient? If it should 

 be found that indexing and cataloguing publications 

 produced by private corporations actually serve a 

 useful purpose, and perhaps relieve "co-operative" 

 organisations of some share of the deficit, should not 

 these publications receive, if not commendation, at 

 least a nod of recognition ? 



I have wondered why men of science, when 

 planning catalogues or classifications, do not consult 

 those who make that work a profession. When 

 people build houses it is generally thought best to 

 consult an architect. 



It may be worth while to note that of the four 

 examples of indexes that you mention, three are now 

 compiled on the alphabetic or dictionary plan. The 

 "Engineering Index," published since 1884, changed 

 from the classified to the dictionary form on the 

 annuals with the year 1919. The "Index Medicus" 

 has just recently changed from the classified to the 

 alphabetic form. We believe the changes were made 

 at the request of librarians who have, through their 

 experience, found the dictionary plan the more 

 serviceable. 



It is to be hoped that in the conference proposed 

 bv Nature, to which representatives of all branches 

 of knowledge are to be invited, librarians and all 

 those who make printed indexes will be included. 



H. W. Wilson, 



President. 



The H. W. Wilson Companv, Publishers of 

 Indexes and Reference Works, 958-964 

 L^niversity Avenue, New York City, 

 .August 6. 



A co-operative index is one published by, or on 

 behalf of, a professional body with the view of secur- 

 ing an adequate standard of efficiency. These indexes 

 are generally based, in part at any rate, upon volun- 

 tary labour. Mr. W'ilson is in error in supjwsing that 

 the main support for abstracts and digests comes 

 from the libraries. It is derived from the subscriptions 

 of members of the professional bodies. Librarians 

 are not qualified to advise on the matter. 



Indexing suffers chiefly from the lack of co-ordina- 

 tion and the insufficient supply of trained workers. 

 It is to secure a proper co-ordination of effort that a 

 conference has been proposed in these columns. The 

 conference should undoubtedly include representatives 

 of the libraries and of the commercial indexes. 



The Writer of the Article. , 



