794 



SCIENCE 



[N.S. Vol. XXV. No. 646- 



all of its near relatives not possessing the 

 character in question. For a time credulity 

 balked and I was compelled to look upon char- 

 acter-units as figures of speech. The origin 

 of forms from a common parent by the loss 

 of -dominancy in its several character-deter- 

 minants accounts for the general presence of 

 a recessive unit, corresponding vrith each 

 dominant unit, in all the nearly related forms. 



No suggestion has been made as to the na- 

 ture of the change by which a dominant allelo- 

 morph becomes recessive, but if this change 

 be looked upon as a degenerative one which 

 may be followed later by complete disappear- 

 ance of the unit it would account for the fact 

 that hybrids between nearly related forms are 

 usually Mendelian, while those between more 

 distant ones are not. 



I may summarize briefly as follows: 



(a) What appear to be unit characters may 

 be, and probably usually are, compound char- 

 acters. 



(l) New characters appear by the change of 

 one or more character determinants from the 

 dominant to the recessive condition. 



(c) Some of the partial products resulting 

 from this process of analysis have no ex- 

 ternally apparent distinguishing characteristic, 

 and these supply instances of so-called ' latent ' 

 characters. 



(d) Mendelian hybridization results in an 

 F^ which is a partial or complete synthesis of 

 an ancestral condition. 



(e) This conception gives an explanation of 

 the general presence of recessive units corre- 

 sponding to the dominant units in each closely 

 related form. 



(f) If the change from the dominant to the 

 recessive condition is a degenerative process 

 which may be followed by complete disappear- 

 ance of a unit, an explanation is found for 

 the fact that Mendelian behavior is a function 

 of nearly related forms but not of more dis- 

 tantly related ones. 



Geoege Hakeison Shull 

 Station fob Expeeimental Evolution, 

 ■ Cold Speing Haeboe, Long Island, 

 December, 1906 



CURRENT NOTES ON METEOROLOGY AND 

 CLIMATOLOGY 



THE LOP-NOR DESERT 



Ellsworth Huntington continues his 

 papers on his recent ecsplorations in Eastern 

 Turkestan with a discussion of ' Lop-Nor — 

 A Chinese Lake,' in the Bulletin of the Amer- 

 ican Geographical Society for February and 

 March, 1907. Additional evidence is adduced 

 regarding what seems to Huntington to be a 

 progressive desiccation of the region within 

 historical times. At Miran the ruins of an 

 ancient Buddhist town, perhaps 1,500 years 

 old, were discovered, covering an area of over 

 five square miles. The town probably had a 

 population of some thousands, but the " mod- 

 ern water supply is only sufScient to support 

 seventy or eighty people." The saline water 

 which the camels have to drink affects their 

 flesh so markedly that the meat becomes 

 ' corned ' by reason of the salt accumulating 

 in the animals' bodies from the water. The 

 journey across the old lake bed was very tedi- 

 ous and difficult by reason of the irregularity 

 of the large rock-salt blocks which cover the- 

 surface. Hunting^ton remarks particularly 

 upon the ability of his camel-man to endure 

 hardship and fatigue with a minimum allow- 

 ance of food and water. On one occasion the 

 man traveled fifty miles in twenty hours with- 

 out nourishment or water. This effect of a 

 desert life in hardening man to the endurance 

 of hunger, thirst and fatigue, as contrasted 

 with the easier, softer life in more humid 

 regions or in oases^ has been commented on 

 by other travelers, notably by Nachtigal some- 

 years ago. The history of Lop-Nor during 

 the last 2,000 years seems to Huntington ta 

 show the following stages: First, a compara- 

 tively large lake, said to measure seventy-five 

 miles each way. Next, during the early cen- 

 turies of the Christian era, an increase in the 

 recorded size of the lake, which can not have 

 been due to diminished use of the rivers for' 

 irrigation, for the population at that time was- 

 larger than at present. Finally, in the last 

 few hundred years there has been a decrease 

 in the size of the lake and in the population 

 about it. It may here be noted that not all' 



