942 



SCIENCE 



[N. S. Vol. XXIX. No. 754 



marks the beginning of researcli on the biol- 

 ogy of soils of the arid regions. Some of the 

 facts gleaned in these studies present such 

 striking features that it was thought wise to 

 make a brief preliminary report on them in 

 this journal. The facts may be categorically 

 enumerated as follows: 



1. Nitrite formation from ammonia com- 

 pounds formed by the ammonifying bacteria 

 has been found to take place markedly at 

 depths of twelve feet in a soil from Haywards, 

 Cal. Further, in samples gathered under the 

 greatest precautious to avoid contamination, 

 nitrite formation was found to go on actively 

 at a depth of five and one half feet in a soil 

 gathered at Eiverside, Cal. Below five and one 

 half feet there was a compact layer of hardpan 

 in which there was little or no bacterial growth 

 and nitrite formation could not, therefore, be 

 expected deeper down in that particular soil. 

 In six other soils collected in different parts 

 of this state nitrite formation was found to 

 depths of six feet or as far down as we had 

 gone for samples. 



2. Contrary to expectations nitrate forma- 

 tion, unlike nitrite formation, has thus far 

 been noted only down to a depth of two feet. 

 Further experiments, however, will be insti- 

 tuted to ascertain if this holds true for all 

 California soils. 



3. A bacteriological examination of a soil 

 from Auburn, kept in a tightly stoppered 

 bottle on the museum shelves for thirty-one 

 years, reveals at least one representative of 

 each of the groups of nitrogen-transforming 

 or nitrogen-assimilating bacteria, except B. 

 radicicola. Of these, several species of am- 

 monifiers were found, one species of nitro- 

 somonas (obtained in the motile and also in 

 the zooglcea form) and one spiecies of Azoto- 

 iacter. The latter exhibits marked differences 

 from the other Azotobacter species thus far 

 described, both morphologically and physiolog- 

 ically, and it was therefore named A. hilgardii 

 in appreciation of the eminent services of 

 Professor E. W. Hilgard to scientific agricul- 

 ture. Briefly, the organism may be described 

 as a small elliptical cell, which forms no pig- 

 ment and only a very thin membrane at the 



surface of mannite solutions. It is non-motile 

 and has a slight nitrogen-fixing power. 



4. The species of nitrosomonas foimd in the 

 old soil mentioned above was fovmd to have 

 spores. This is particularly interesting, since 

 Winogradsky stated in a report of results of 

 his wonderfully thorough experiments on the 

 nitrifiers, that spores were never observed. 



No Nitrohacier species or nitrate organism 

 has as yet been found in the old soil. 



The above facts are probably due chiefly to 

 the great perviousness of the soils of the arid 

 region, owing to the very slow formation of 

 clay substances; whereby moisture, air and 

 roets are enabled to penetrate to depths rarely 

 found in the hmnid regions. 



Chas. B. LiPMAN 



Laboeatoby or Son. Bacteeiology, 

 UNryERSiTY OF Caxitoenia, 

 May 12, 1909 



A SCHEME TO REPRESENT TYPE HEREDITY IN MAN 



Efforts to reconcile Mendel's laws with the 

 prevailing views of blended effects in heredity 

 need not be unavailing, if the two may be con- 

 sidered as phases of the same process acting 

 at different times during the life history of 

 an elementary species.' 



Heredity represents all the changes of or- 

 ganic life by three factors : 



1. Determiruints, which are in the germ 

 plasm. 



2. Modifiers, which are all influences 

 through time and space that act on the germ 

 plasm, and 



3. Laws of change, which are the rules of 

 conduct by which the determinants and the 

 modifiers interact. 



These factors are variable when looked at 

 through all space and during all time, but 

 for any elementary species in a given space 

 and for a limited time they are fixed. 



I present herewith a tentative scheme to 

 supplement my theory of heredity.' 



D and R represent homozygotes of an 



•Spillman, Science, N. S., Vol. XXVII., 1908, 

 pp. 47-57. 

 ' Bean, Philippine Journal of Science, 1908. 



