1905] CURRENT LITERATURE 303 
usually been considered uncommon, he has found to result regularly in seventeen 
of the hybrids that he reports. Races which show the possession of such latent 
characters that are externalized as a result of crossing he has designated in another 
recent paper? as “‘cryptomeric” races, and the process of externalization of 
latent characters as ‘‘cryptohybridism.” In many cases the new characters are 
recognizable as atavistic, in other cases they appear to be retrogressive or degres- 
sive modifications. The processes by which these arise he calls ‘“‘hybrid atavism” 
and “hybrid mutation,” and he looks upon the latter as an important source of 
new forms, especially of ‘‘defect-races.”’ 
In nearly all cases the new characters as well as the parental characters 
behaved in a Mendelian way. Thus in a cross between-two races of peas, white- 
flowered X rose-colored gave complete dominance of red (atavistic) in the first gen- 
eration (F;) splitting in F, to red: rose: white =9: 3: 4, the red dominating the rose, 
and red+rose the white, in the simple ratio 3:1. In a case of this kind the red 
is called ““dominant” and rose “co-dominant.” In other cases “co-recessives” 
occurred, giving four forms in the second generation, the ratio being 9:3:3:1 
A still further complication was found in a cross between white-flowered Matthiola 
glabra and red-flowered M. incana, in which pure violet dominated in F, and five 
forms appeared in F,, giving approximately the proportions 27:9:9:3:16. 
This last result was reported by TSCHERMAK two years ago, and he explained it 
by assuming that each of the four colors (the fifth class being the white reces- 
Sives) is a compound, a+b, a+d, b+c, and c+d, and on this assumption he 
predicted then what would be the product of each of these groups in F; when self- 
fertilized. The third generation is here presented, showing that in every instance 
his prediction was confirmed. 
Lock" obtained very similar results in crosses of various cultivated peas with 
Species native at Peradeniya, Ceylon. Thus with respect to seed-color, self- 
colored x white gave in F, self-colored : purple spotted : white=9: 3:4, and 
another case precisely resembling that of TSCHERMAK’s Matthiolas gave 
Categories of seed-coloration in the second generation nearly in the ratios 27:9: 
9:3:16. The explanation offered by Locx is essentially the same as TSCHER- 
MAK’S, though differently expressed. He assumes that the allelomorphs ABC 
in the colored pea are matched by corresponding recessives abc in the white, but 
that neither B nor C can reach external expression except in the presence of A. 
he chance combinations of gametes containing these allelomorphs then result 
In the observed ratios 
; Lock’s paper gives an admirable general treatment of Mendelism, illustrated 
With new examples taken from his own studies, and presents briefly but fairly 
the results of other workers. It can be recommended to any one who wishes to 
at =, 
| PSCHERMAK, E., Die Theorie der Kryptomerie und des Kryptohybridismus. 
Beihefte Bot. Centralbl. 16: 11-35. 1904. 
P tennan R. H., Studies in plant breeding in the tropics. Ann. Roy. Bot. Gard. 
erade 
niya 2: 209-356. 1904. 
