686 



SCIENCE 



[N. S. Vol. XLIII, No. 1115 



there at the beginning of the next academic 

 year. Dr. William S. Foster, now instructor 

 in psychology in Cornell University, has been 

 made assistant professor of education. 



DISCUSSION AND CORRESPONDENCE 



THE ORIGIN OF PACIFIC ISLAND FAUNAS 



To THE Editor of Science: In the current 

 number of Science (April 14) I read with in- 

 terest the abstract of a paper by Dr. Pilsbry 

 on the land shells of the Pacific islands as a 

 guide to former geographic conditions. The 

 author rejects "the hypothesis that Pacific 

 snails reached the islands by oversea drift " be- 

 cause it " leaves the absence of higher snails 

 unexplained." 



It is perhaps dangerous to criticize an argu- 

 ment from an abstract, but as this point has 

 been cited in other cases where I know it in- 

 volved a fallacy, I venture to suggest that 

 Doctor Pilsbry may also have overlooked the 

 fact that the older a given group is the longer 

 time there has been for the chances of over- 

 sea dispersal, hence the greater the probability 

 of its reaching the more remote islands. Obvi- 

 ously a group which has not become dominant 

 until the later Tertiary has but a very small 

 chance of having reached remote islands as 

 compared with a group that was dominant 

 during the Mesozoic or earlier. Certain fea- 

 tures in the Mesozoic and early Tertiary cli- 

 mates would tend to increase greatly the 

 chances of oversea transport, and a third ex- 

 planation might be cited in the differences of 

 habitat which would tend to facilitate the 

 drift dispersal of some types more than others. 

 That the higher types should be found in the 

 larger islands and those nearer to the conti- 

 nental platforms is quite to be expected; and 

 by the law of chances, where only a limited 

 nmnher of primary stocks of the more ancient 

 groups have reached the more distant islands, 

 one ought not to expect to find any of the 

 groups of comparatively recent dominance. 



With many if not most groups of land inver- 

 tebrates, as with the land vertebrates, the evo- 

 lution and dispersal of the modern dominant 

 fauna took place during the Tertiary, and 



much of it I suspect rather late in the Ter- 

 tiary. But, as also with vertebrates, the wide 

 oceanic dispersal of the older or lower groups 

 may be due more to their greater facilities for 

 dispersal than to their greater antiquity. 



W. D. Matthew 



BELGIAN HARE, A MISLEADING MISNOMER 



In a paper entitled " Anatomical Adapta- 

 tions in the Thoracic Limbs of the California 

 Pocket Gopher and Other Eodents,"i Charles 

 Daniel Holliger has identified the so-called 

 Belgian hare as Lepus europaeus (p. 449). 

 At various places in the text and particularly 

 in the last paragraph of the summary (p. 489) 

 he comes to the conclusion that " domestica- 

 tion reduces specialization " and that " the 

 typical cursorial modifications [of the Jack 

 rabbit] have either disappeared or have been 

 much reduced in the Belgian hare." 



As a matter of fact the " Belgian hare " is a 

 domestic variety of the European rabbit and 

 the striking differences observed by Holliger 

 are due to inherent generic differences, the 

 Jack rabbit belonging to the genus Lepus and 

 the European rabbit and with it the Belgian 

 hare belonging to the rather conspicuously 

 different genus Oryctolagus? Or to put it 

 the other way around, the striking differences 

 observed by Holliger (see especially table p. 

 487) are part of those on which the genera 

 Lepus and Oryctolagus are founded. 



M. W. Lyon, Jr. 

 George Washington University 



the VAPOR PRESSURE OF SOLUTIONS 



In Science of January 14 last Arthur Tabor 

 Jones describes an apparatus for observing the 

 change in the volume of solutions in the pres- 

 ence of the solvent owing to the difference in 

 the vapor pressures. He could not determine 

 the rate of change owing to the roughness of 

 the bell jar. The following apparatus has 



1 Vniv. Calif. Pub]., Vol. 13, pp. 4A7-iQl, March 

 7, 1916. 



2iSee Lyon, Smiths. Miscell. Coll., Vol. 45, pp. 

 323, 406, pi. 98, June 15, 1904; and Miller, Cat. 

 Museum West. Europe Brit. Mus., p. 485, Novem- 

 ber 23, 1912. 



