440 THE AMERICAN NATURALIST [VOL. XLII 



was taken with Lock 5 regarding his assumption that 

 novelties which appeared in crosses between certain peas 

 were due to inactive units which became active on cross- 

 ing. Lock 6 has since reconsidered that case and inde- 

 pendently come to the same conclusion that I reached, 

 namely, that the spotted seed-coat was introduced by the 

 white-coated pea in which it was invisible owing to its 

 separation from the pigment-producing factor. This is 

 not an uncommon type of latency and seems to be the 

 only type included by writers who have treated the sub- 

 ject of latency from the Mendelian view-point. It gives 

 rise to such modifications of the Mendelian ratios as 9 : 3 : 4, 

 9:7, 27:9:9:3:16, 27:9:28, etc., instead of the theo- 

 retical 9:3:3:1 and 27:9:9:9:3:3:3:1. Some of these 

 modified ratios are of more common occurrence, and are 

 more familiar, than the unmodified ones, perhaps owing 

 to the fact that albinism has been so frequently involved 

 in the Mendelian investigations. Characteristics which 

 are rendered latent by separation in the course of Men- 

 delian hybridization have been called "masked" char- 

 acters by Punnett. 7 This is not a particularly apt term 

 for latent characters of this type, and would be much 

 more appropriately applied to cases of latency due to 

 hypostasis discussed below. 



LATENCY DUE TO COMBINATION 



The existence of mottling as a latent characteristic in 

 pigmented beans, due to the fact that it only becomes ap- 

 parent when in the heterozygous condition, is obviously 

 of an entirely different type. Instead of being a phe- 

 nomenon of separation, it is due to the union in the 

 same zygote, of two dominant allelomorphs, either of 

 which alone will produce a manifest character, but 



5 Lock, K. H. Studies in Plant Breeding in the Tropics. Ann. Eoy. Bot. 

 Gard. Peradeniya, 2, pp. 299-356, 1904. See p. 241. 



'Lock, E. H. On the Inheritance of Certain Invisible Characters in 

 Peas. Proc. Eoy. Soc., B, 79, pp. 28-34, 1907. 



7 Punnett, E. C. Mendelism. 2d ed., pp. viii + 85, 1907, London : Mac- 

 millan & Co. See pp. 47-53. 



