Decembeb 29, 1905.] 



SCIENCE, 



879 



The result is exactly the same as when a so- 

 called ' pure ' Mendelian gray mouse is ob- 

 tained through a cross. The ' pure ' dominant 

 is contaminated in the same sense as the 

 ' pure ' recessive and in the same way. For 

 example, a gray mouse crossed with a black 

 will give a mouse CGCB whose germ cells 

 will be, on my view, CG(CB) and (CG)CB. 

 Such mice inbred will give 

 ICaiCB) +2C0{CB) (GG)CB + 1 {CG)GB. 



The so-called 'pure' dominant, CG(GB), is 

 really only a dominant gray with black in 

 the latent condition. This form is strictly 

 comparable to the yellow mice that Cuenot 

 tested for purity, and could not be expected 

 to give by inbreeding a form with perfectly 

 pure germ cells, GGCG. To obtain such a 

 pure gray mouse, CGGG, a wild form, never 

 crossed with black, must be sought; for, once 

 crossed always contaminated. 



The preceding results given for these special 

 cases are strictly in accordance with what is 

 now becoming recognized in regard to the 

 usual condition of albino mice. It has been 

 shown that these carry gray, or black, or some 

 other color latent. Thus a white mouse is 

 A(G) or A(B) or A(Y). Suppose one of 

 these white mice, with the formula A(G), is 

 crossed with a pure gray mouse, with the 

 formula CG: 



A(G) X CG = A{G)GG. 

 The offspring are all gray, because free gray 

 dominates free white. Suppose now we in- 

 breed these A(G)CG mice. Their germ cells 

 will be, on my point of view, of two sorts, 

 viz., A(G)(OG) and (A(G))CG. The result- 

 ing offspring give 



lAiG){GG) + 2A{G) (GG){A{G))GG 



White Gray +1{A{G))GG. 



Gray 



Since albino is white, while stands for 

 the color with which it is associated, we may 

 simplify the form of the equation by omitting 

 the C"s and putting the (r's together, thus: 



IA{G) -\-2A(G) {A(G))G+l(A{G))G. 



Thus our formula gives the Mendelian 

 results, but it also brings to light the different 

 relation of latent (G) and free G. If 



individuals of the middle group above be 

 inbred, they again give the Mendelian ratio 

 1:2:1; because the free A and the free G 

 alternately dominate and become latent, so 

 that the germ cells are A(G) and (A)G. 



It is needless to go over the well-known 

 Mendelian combinations of other sorts, back 

 crossing, etc., since they also work out accord- 

 ing to our formula. 



The important point is not that there is 

 offered here a new set of Mendelian formulce, 

 hut a new conception regarding dominance 

 and recessiveness, ivhich I Relieve to he hetter 

 in accord with the conditions found to exist 

 in extracted recessives. Furthermore, this 

 idea hrings into question the assumption of 

 the so-called purity of the germ cells, hy 

 means of which modern writers are explaining 

 the Mendelian results. Purity only means 

 dominance over latency. Dominance over 

 recessiveness follows a different rule, viz., the 

 rule of alternation or of contrasted gametes. 



T. H. Morgan. 



RECENT CHANGE OF LEVEL IN ALASKA.^ 



About the middle of September, 1899, the 

 coast of Alaska, in the St. Elias-Fairweather 

 region, was visited by a series of vigorous 

 earthquake shocks, one effect of which was 

 to greatly modify the front of the Muir gla- 

 cier, and to fill Muir Inlet with ice dislodged 

 from the glacier. ~ The shocks were also felt 

 with marked intensity at Yakutat, and a com- 

 pany of prospectors, camped near the Hubbard 

 glacier in Disenchantment Bay, report a series 

 of severe shocks and accompanying water 

 waves. 



^ The observations outlined in this paper were 

 made in the summer of 1905 in connection with a 

 general geological survey of the Yakutat Bay 

 region by a United States Geological Survey party 

 under the direction of the senior author. A 

 grant of money obtained through the assistance 

 of the American Geographical Society made it 

 possible to add the junior author to the party as 

 special assistant in physiographic and glacial 

 geology. Acknowledgments are due to B. S. 

 Butler, the other member of the party, for assist- 

 ance in this work. Published by permission of 

 the Director of the U. S. Geological Survey. 



