April 15, 1904.] 



SCIENCE. 



629 



these soils as the Bureau of Chemistry obtained 

 by five hours' extraction with dilute acid of 40 

 degrees centigrade. 



This correction will be made in tlie third 

 edition of Illinois Circular No. 72. Analyt- 

 ical chemists will recognize how little force 

 there is in this single just criticism in its 

 application to the principles under discussion. 



To illustrate his difficulty in finding suit- 

 able material for criticism, Doctor Cameron 

 says : 



It is not at all clear why the phosphorus as 

 determined in the two investigations should be 

 compared on the basis of an acre surface with a 

 depth of seven inches, for it is inconceivable that 

 any one at this day, and in view of the well-known 

 work of Darwin and others, would suppose that 

 the same identical seven inches of soil would 

 remain at the surface for any considerable period 

 of time. 



This criticism is neither pertinent nor con- 

 sistent. First, it may safely be assumed that 

 neither earthworms nor crawfish were active 

 in these particular samples of soil during the 

 interval between the two investigations, hence 

 the criticism has no bearing on the point. 

 Second, all results and comparisons reported 

 in Bulletin 22 of the Bureau of Soils are 

 based upon soil samples taken to certain 

 depths; hence the critic is inconsistent. Re- 

 ports of soil investigations which are written 

 for the benefit of agriculture and agricultural 

 people are best given on the acre basis, because 

 this is the basis used in raeasuring crop yields, 

 in applying manure, fertilizers, etc. The 

 classic agricultural investigations of Lawes 

 and Gilbert are practically all reported on the 

 acre basis. Seven inches is a common depth 

 for good plowing and this method of report- 

 ing results is in accord with the methods* 

 adopted by the Association of Official Agri- 

 cultural Chemists for collecting soil samples, 

 which recognize that there are differences be- 

 tween soils and subsoils, whereas the arbitrary 

 method of soil sampling, 0-12 inches, 12-24 

 inches, and 24r-36 inches, in depth, as iised 

 by the Bureau of Soils (see pages 23-33 of 

 Bulletin 22) commonly mixes surface soil 

 and subsoil in one of the samples. 



* U. S. Depai'traent of Agriculture, Bureau of 

 Chemistry, Bulletin 67, p. 152. 



While it is true that, in the early publica- 

 tion of his paper, Doctor Hilgard anticipated 

 the proceedings of the Association of Amer- 

 ican Agricultural Colleges and Experiment 

 Stations and of the censorship of the Bureau 

 of Soils over the publication of those pro- 

 ceedings, it is also true that his arguments 

 are unanswerable, as are, likewise, those of 

 Director Hall of the Eothamsted Experiment 

 Station, whose criticism of Bulletin 22 ap- 

 peared in Nature last November, although it 

 is entirely ignored by Cameron. 



Cyril G. Hopkins. 



College op Agricijltuee, 

 University of Illinois. 



SPECIAL ARTICLES. 



ON A LEPTOCEPHALUS OF THE CONGEE EEL.* 



DuEiNG late July, 1900, the first eel eggs 

 taken outside of Italian waters were secured 

 by the Eish Commission schooner Grampus 

 on the surface of the Gulf Stream off New- 

 port. The development of these eggs was de- 

 scribed in the Bulletin of the U. S. Eish Com- 

 mission for 1901. 



The largest larva reared measured about 

 11 mm. in length. The larvae were charac- 

 terized by the projecting lower jaw, the ar- 

 rangement of the spots and the number of 

 protovertebrse. Since writing the account 

 which appeared in the bulletin the larvae have 

 been mounted on slides and a more satisfac- 

 tory count of the protovertebrre made possible. 

 There is still some doubt about the number of 

 caudal protovertebrfe. The count as near as it 

 is possible to get it is 64 + 86, 64 + 91, 66 -|- 

 89, 67 + 82, 67 -|- 89, 68 + 81 and 70 + 86 in 

 seven larvas. 



On July 31, 1902, the Grampus collected a 

 Leptocephalus 65 miles south of No Mans 

 Land. It has a total leng-th of 21 mm. and 

 is undoubtedly the same species reared at 

 Woods Hole in August, 1900. It agrees 

 with the 1900 specimens in the projecting 

 lower jaw, the general plan of the coloration, 

 and has approximately the same number of 

 protovertebrse. The protovertebrse are defi- 

 nitely 73 for the abdominal portion of the 



* Contributions from the Zoological Laboratory 

 of Indiana U"i-"ersity, No. 54. 



