No. 1, May, 1921] GENETICS 31 



are pointed out and figured, but the characters utilized in comparing Florida-grown offspring 

 with Bahama ancestry are shell characters. Differences in general coloration, mottling, and 

 ridging of the shells are mentioned. The characters used as standards of comparison are 

 numerical characters, numbers of whorls, altitude, and greatest diameter of the shell. A 

 check series (100) of each of the species transplanted, and all the measured first and second 

 generation Florida-grown offspring, are figured in plates and the individual measurements are 

 all given in tables. — While in most of the series of first and second generation Florida-grown 

 material one notes that the mean altitude is greater and the mean greatest diameter is less 

 than in the original Bahama material, no great changes are seen in the means or in the ranges 

 of variation of the characters studied. No biometrical treatment of data has been employed. 

 The author concludes that the different species of Cerions seem to be quite stable within 

 their normal limits of variation and appear to adhere to these limits even when subjected to a 

 decidedly changed environment. — Hybrids were obtained between transplanted Bahama 

 Cerion viaregis and the native Florida-key Cerion incanum . In shell measurements the author 

 finds the hybrids intermediate and somewhat more variable than the parent species. In 

 coloration, character of ridging, and general shape of shell the hybrids are extremely variable. 

 Some are so mottled as ver\' strongly to resemble the mottled Cerion martensi group; in gen- 

 eral character of ribbing the range was from the relatively smooth Cerion incanum to the 

 rough Cerion viaregis; the range in general form was likewise from the somewhat cylindrical 

 Cerion incanum to the more conical Cerion viaregis. What is of even greater interest, these 

 variations are independently combined in the hybrid offspring. Attention is called to cases 

 in which species in a certain region are sometimes found to be extremely variable. "Prior to 

 this year I was more and more inclined to the belief that we might possibly find that these 

 very abundant and variable forms might represent new ingressions into a faunal area in 

 which conditions for their existence were optimum to an unusual degree, where the normal 

 death rate, due possibly to an absence of natural enemies, might be reduced, and where 

 all the factors involved were inclined to favor the new arrival to the utmost, and that these 

 factors and the necessarily reduced inbreeding might be responsible for the loosening of spe- 

 cific bounds and the producing of variants which, in the course of time, might result in a 

 state of flux. — "Our Cerion experiments on Newfound Harbor Key, however, throw a new 

 light upon the case, for here we have produced a state of flux by cross-breeding. There is no 

 question that if we did not know the true inwardness of the Cerion complex as it exists at the 

 present time in our colony upon this key, we would treat the material as we have treated such 

 assemblages in the past; that is, as a very variable species. It therefore seems proper to 

 assume that the converse should receive an equally favorable consideration, for it seems fair 

 to believe that further breeding experiments will prove that such complexes are the product 

 of cross-breeding. — A. M. Banta. 



226. Bateson, W. Genetic segregation. Proc. Roy. Soc. London B, 91 : 358-368. 1920.— 

 Segregation is a phenomenon which is not limited to particular classes or kinds of characters. 

 The factors governing segregation of quantitative characters either do not segregate cleanly 

 or the numbers involved are so large that their effects are not clearly shown. In many 

 crosses involving quantitative characters, v/hich appear to segregate cleanly, one or the other 

 original type fails to reappear in its entirety. The author favors the first explanation sug- 

 gested. Factor groups or complexes may sometimes segregate as units, sex determination 

 and irregularities of inheritance in Oenothera are mentioned as being due to such a phe- 

 nomenon. In other cases these complexes may break up and are then responsible for the 

 appearance of mosaics of secondary sexual characters in fowls and different classes of color 

 mosaics in the snapdragon and sweet pea. Linkage between factors conditioning the several 

 character components of the mosaics is seldom evidenced and the question is raised if they 

 are all distributed among different chromosomes. The author protests the general applica- 

 tion of Morgan's theor}^ regarding crossing over and the limitation of linkage groups on 

 the ground that it has been proven for only one case — Drosophila. The theory of linkage 

 and crossing over has assumed much regarding the physical behavior of the chromosomes that 

 cytology cannot substantiate. In plants the time of segregation is not limited to the reduc- 



