1010 



SCIENCE 



[N. S. Vol. XXV. No. 652 



seem to be out of all proportion to the actual 

 differences between the adult genera or species. 



The facts would seem to force us, if we still 

 cling to the idea that in chromosomes we are 

 to find specific morphogenic substances, to 

 some such postulate as the one already sug- 

 gested, that only the more superficial and 

 fluctuating qualities are borne in the chromo- 

 somes, for then we might appreciate how con- 

 siderable fluctuation in the number of chro- 

 mosomes in different species might be recon- 

 cilable with the relatively smaller differences 

 between the adults. 



However, this idea of the respective roles of 

 cytoplasm and nucleus in inheritance was of- 

 fered only as a suggestion, and not as a theory 

 and such it must remain, unless some more 

 convincing evidence is forthcoming. Its only 

 value in this connection is to show that we are 

 not restricted to a consideration of the chro- 

 mosomes as the sole vehicle of heredity, and 

 that equality in the amount of chromatin con- 

 tributed by each parent, even should we suc- 

 ceed in assigning heritable qualities to the 

 chromosomes, does not necessarily imply that 

 we inherit equally from each parent. 



Michael F. Guyer 



Uni^'eesitt of Cincinnati, 

 March 12, 1907 



THRUSTS AND RECUMBENT FOLDS, A SUGGESTION 

 BEARING ON ALPINE STRUCTURE * 



Let it be assumed that as a result of a 

 shearing strain a thrust fault, A, is initiated 

 in the crystalline basement of a sedimentary 

 series, and that displacement occurs along a 

 plane which rises at a gentle angle to the 

 plane of stratiflcation. Let it be assumed 

 further that the strata comprise a soft shale 

 overlain by a limestone of moderate thickness, 

 above which is a thick series of sediments. 



The immediate effect on the shale will be 

 to thicken it in front of the overthrust crystal- 

 lines (as was repeatedly observed in the case 

 of soft layers under similar conditions of pres- 

 sure in experiments on folding described in 

 the Thirteenth Annual Report of the U. S. 

 Geological Survey). In swelling the shale 



^Eead before the Geological Society of Wash- 

 ington, April 10, 1907. 



itnnwiii»!i^ii>»/inn.'.u»inii!N.'iiy'i,wln/!n!iuii!t:>!i»>iiir7m^. '^rT-r^-^is^^ 



Fig. 1. Hypothetical Development of Recum- 

 bent Folds from Overthrust Faults. 



will have somewhat the effect of a laccolithic 

 intrusion and will raise the overlying lime- 

 stone, forming an anticline. 



If the plane of the thrust forms an acute 

 angle with that of the bedding, the shear 

 may follow the bed of shale, thus separating 

 the limestone and overlying strata from the 

 underlying; and the stress transmitted by the 

 advancing tongue of gneiss to the limestone 

 may roll the latter back upon itself. The 

 overlying strata would become more or less 

 involved in the overfold. 



The recumbent fold will develop to a length 

 determined (1) by the competency of the 

 strata to transmit thrust; (2) by the effect of 

 the resistance, which increases as the strata 

 pile up; and (3) by the conditions favoring 

 the development of a second thrust fault, B. 



If the movement continues to the produc- 

 tion of a second thrust, B, the plane of the 

 thrust. A, and the recumbent beds will be 

 raised into an anticlinal attitude, as the flat 

 strata were in the first instance. Thus the 

 point of the overturn, M, will appear to be 

 bent downward, and if movement continues 

 on the thrust. A, it may become bent under. 

 Such movement could not, however, continue 



