January 9, 19 13] 



NATURE 



527 



results of five years' work which has involved thirteen 

 generations and several thousand individuals. Two 

 verv definite results have been obtained, and it is 

 important that these should be grasped at the outset, 

 viz. : (i) that the record of egg-production of a hen 

 is not of itself a criterion of any value whatsoever 

 from which to predict the probable egg-production 

 of her female progeny — in short, there is no correla- 

 tion between the egg-production of individuals and 

 either their ancestors or their progeny ; (2) notwith- 

 standing the above-mentioned fact, fecundity is, in 

 some manner or other, inherited in the domestic fowl. 



The mere fact that a fowl is anatomically normal 

 is not sufficient to ensure the laying of eggs ; two 

 physiological factors or groups of factors are essen- 

 tial. The first of these is termed the " normal ovula- 

 tion " factor, i.e. the complex physiological characters 

 which in their entirety determine the normal repro- 

 ductive activity and definite periods of productivity, 

 wjiat are termed the winter and summer cycles, de- 

 pending upon differences in the complex physiological 

 mechanism concerned with the maturation of the 

 oocytes and ovulation. 



Winter egg-production is chosen as the basis of 

 measure, representing as it does the cycle in which 

 the widest difference is found between birds of high 

 and low fecundity. Three \yell-defined classes are 

 apparent ; these include birds with high winter re- 

 cords, those with low, and those that do not lay at 

 all. In respect to these three divisions there is a 

 definite segregation in the Mendelian sense. 



-As the result of considerable work supported by a 

 mass of evidence, the author concludes : — 



There are three distinct and separately inherited 

 factors upon which fecundity in the female fowl 

 depends. 



The first of these factors (which may be called the 

 •anatomical) determines the presence of an ovary, 

 the primary organ of the female sex. The letter F 

 is used throughout to denote the presence of this 

 factor. 



There are two physiological factors. The first of 

 these (denoted by L.) is the basic physiological factor, 

 which, when present alone in a zygote with F, brings 

 about a low degree of fecundity (winter record under 

 thirtv eggs). This factor is under no limitations in 

 gametogenesis, but may be carried in any gamete, 

 regardless of what other factors may be also present. 



The second physiological factor (denoted by L,), 

 when present in a zygote together with F and L,, 

 leads to a high degree of fecundity (winter record 

 more than thirty eggs). When L^ is absent, how- 

 ever, and Lj is present, the zygote exhibits the same 

 general degree of fecundity (under thirty) which it 

 would if L, were present alone. These two inde- 

 pendent factors, L, and L„, muse be present together 

 to cause high fecundity, either of them alone, whether 

 present in one or two "doses," causing the same 

 deffree of low fecundity. 



The second physiological factor, L,, behaves as a 

 sex-Hniited (sex-correlated or sex-linked) character, in 

 gametogenesis, according to the following rule : the 

 factor L„ is never borne in any gamete which also 

 carries F. That is to say, all females which bear L,, 

 are heterozygous with reference to it. Any female 

 mav be either homozvgous or heterozvgous with re- 

 spect to L,. Anv male may be either homozygous or 

 heterozygous with reference to either L,, L„, or both. 



Numerous other matters of great interest are lucidly 

 set forth, to which want of space forbids us to refer 

 The whole piece of work is an e.Kcellent example of 

 the practical application of Mendelian principles to 

 an important economic question, and deserves most 

 r.-'reful studv. Waithr E. Collinge. 



NO. 2254, VOL. go] 



EGYPTIAN SODA. 



A REPORT by Mr. A. Lucas on "Natural Soda 

 Deposits in Egypt " has been issued by the 

 Ministry of Finance as "Survey Department Paper, 

 No. 22." Natural soda occurs' in Egypt principally in 

 the Wadi Natrun in the Libyan desert, but it is also 

 found some fifty kilometres due north of this, at El 

 Barnugi, in Lower Egypt, and at Mahamid, in Upper 

 Egypt. The principal soda-lakes are in a valley the 

 bottom of which is about 27 metres below sea-level ; 

 the lakes extend over a range of 30 kilometres, the 

 nearest being about 38 kilometres from the Nile. In 

 ancient times there were two lakes, which became 

 united when water was most abundant, but at the pre- 

 sent time they are divided into about a dozen separate 

 areas, the smaller of which dry up almost entirely in 

 summer, leaving only a few pools of water. The soda 

 is found in solution in the water of the lakes, in 

 a solid form at the bottom of some of the lakes and 

 as an incrustation on the adjoining ground. 



Analyses of the water are given for ten of the twelve 

 lakes. In the case of the most concentrated the 

 figures were: — Specific gravity, i'26o; Na^CO,, 62'i5; 

 NaCl 252-35; Na„SO^, 64-54; to'^l 37904 grams per 

 litre. The "lakes are largely fed by springs in the bed 

 of the lakes, but also by water trickling in fromthe 

 surrounding ground. At low water one of the springs 

 is so powerful that a boat trying to pass over it is 

 driven forciblv back; another spring, round whichan 

 iron cylinder had been placed, was found to be flowing 

 at a height of So centimetres above the lake level at 

 the end 'of February. These springs flow energetic- 

 ally all the year round, but in one case at least there 

 is 'increased activity about October. Analyses of the 

 spring and well -water showed total solids ranging 

 fromV3 to 4-6 grams per litre, the quantity of soda 

 ranging from 0^2 to r2 grams per litre, almost all in 

 the form of bicarbonate; it is therefore probable that 

 the soda is carried into the lakes by the inflowing 

 water, and is there concentrated by evaporation. 



The water-level in the lakes falls in summer, begins 

 to rise again in October, and reaches a maximum in 

 March. This variation might be attributed to the 

 different rates of evaporation in summer and in 

 winter; but there appears to be a definite increase of 

 flow in October; this precedes the slight autumn 

 rains, and must be due to an increased flow of under- 

 ground water. The underground flow is from the 

 north-east, in which direction the Nile lies nearest; 

 this is also the side on which the visible flow into the 

 lakes takes place. The fact that the lakes fall whilst 

 the Nile is rising, and conversely, may be due to lag ; 

 in the case of some wells in the neighbourhood of 

 Cairo, under constant observation for thirteen years, 

 the time required for the water-levels to be raised by 

 the influence of the Nile flood varied from 25 to 55 

 metres per day. 



The lakes deposit both salt and soda. The former 

 is practically pure, at least after washing; the latter 

 consists mainly of the compound 



Na„C03,NaHC03,2H,0, 

 but mav contain an excess either of carbonate or of 

 bicarbonate; it is often mixed with large quantities of 

 salt (from 2 to 27 per cent.), and of sodium sulphate 

 (from o to 39 per cent.). 



The salt is probably of marine origin. _ The large 

 excess of sulphate and the absence of iodides and 

 bromides may be explained by the separation of 

 I gvpsum and of salt on partial evaporation, and the 

 ■ subsequent washing away of the mother-liquors, e.g. 

 by a fresh influx of sea water. The conversion of 

 chloride and sulphate into carbonate and bicarbonate 

 has been explained as due to a reversal of the usual 



