SCIENCE 



[N. S. Vol. XLIV. No. 1141 



egg production per unit of time in the lacto- 

 phosphate females is nearly 5 times as great 

 as in the controls. 



A further point of interest is that if a very- 

 small dose of corpus luteum substance 2 be ad- 

 ministered to the birds each day along with the 

 calcium lactophosphate the stimulating effect 

 of the latter upon the growth of the females 

 is completely inhibited. 



It has been known that the internal secre- 

 tions of certain organs might have a different 

 effect upon the growth of males and females, 

 and indeed in the present series of experi- 

 ments we have seen such a differential effect 

 following the feeding of several different gland 

 substances. It is another thing, however, to 

 find inorganic salts exercising such a differ- 

 ential effect. It furnishes one more pieee of 

 evidence of the deep-seated biochemical differ- 

 ences which underlie sex differences, and at 

 the same time is in line with the medical evi- 

 dence as to the great importance of calcium in 

 the physiology of the reproductive organs of 

 the female. Raymond Pearl 



October 31, 1916 



THE PRESENT STATUS OF THE DOLOMITE 

 PROBLEM 1 



The problem of the origin of the dolomites 

 and dolomitic limestones has long occupied 

 the minds of geologists and many theories 

 have been advanced for their formation. But 

 no one of these has been universally accepted. 

 The chief theories which have been proposed 

 are briefly as follows: First, the alteration 

 theories which assume that dolomites have 

 been formed by the partial replacement of 

 limestones by magnesia either (1) before they 

 emerged from the sea, through the agency of 

 sea-water, or (2) subsequent to their emerg- 

 ence through the agency of ground-water. 

 Second, the primary deposition theories which 

 maintain that the dolomites were originally 

 deposited in the form that they now appear, 

 (1) by chemical precipitation from the sea, or 



a A material which I have earlier shown (Jour. 

 Biol. Chem., Vol. XXIV., pp. 123-135, 1916) to 

 have a retarding or inhibiting effect upon the 

 growth of the chick. 



i A more complete report on the origin of dolo- 

 mite will appear in Vol. XXV. of the Iowa Geo- 

 logical Survey, which is now in press. 



(2) by the deposition of clastic grains of dolo- 

 mite derived from the disintegration of older 

 dolomitic limestones. Third, the leaching 

 theories which are based on the well-known 

 fact that during the weathering of a dolomitic 

 limestone the lime is removed more rapidly 

 than the magnesia, thereby causing an enrich- 

 ment of the latter constituent. This leaching 

 is supposed to take place either (1) through 

 the agency of sea-water prior to emergence, or 

 (2) through the agency of atmospheric water 

 after the limestone has become a part of the 

 land. 



The marine alteration theory is by far the 

 most widely held to-day, but the chemical pre- 

 cipitation theory has many champions. 



The writer was led to suspect several years 

 ago, that a careful field study of dolomitic for- 

 mations would throw some light upon their 

 origin and through the aid of the Iowa Geo- 

 logical Survey and an appropriation from the 

 Esther Herrman Research Fund of the New 

 York Academy of Sciences he has been able to 

 examine nearly all of the important dolomites 

 of the Mississippi Valley and the eastern 

 United States. 



These studies have furnished irrefutable 

 evidence that the majority of the dolomites 

 examined have resulted from the alteration 

 of limestone. The following facts support this 

 contention: (1) the lateral gradation of beds 

 of dolomite into limestone, sometimes very 

 abruptly; (2) the mottling of limestones on 

 the border of dolomite masses by irregular 

 patches of dolomite; (3) the existence of rem- 

 nants of unaltered limestone in dolomite, and 

 of nests of dolomite in limestone; (4) the ir- 

 regular boundaries between certain beds of 

 limestone and dolomite; (5) the presence of 

 altered oolites in some dolomites; (6) the pro- 

 tective effect of shale beds; and (7) the par- 

 tial obliteration of original structures and tex- 

 tures in many dolomites and dolomitic lime- 

 stones. 



Concerning the conditions under which 

 the dolomitization took place there are 

 many reasons for believing that the more ex- 

 tensive dolomites have all been formed be- 

 neath the sea prior to or contemporaneously 

 with recrystallization and that the dolomitiza- 



