DAIEY FAKMING — DAIRYING. 275 



hybrids in respect to each pair of contrasted cliaracters is a reaction or response 

 in tlie cells, and is not due to a material segregation of the two kinds of materials 

 contributed by the germ cells of the two parents. The reaction differs in the 

 germ cells of the hybrid from that of either of the parental types because the 

 material basis of the germ cells differs owing to its dual origin. The results 

 are due, how'^'er, to difference in reaction and not to a separation of mixed 

 materials. The general point of view that underlies this conclusion is epi- 

 genetic, while the contrasting view, that of separation of materials, is essen- 

 tially one of preformation. . . . 



" The old view that sex is determined by external conditions is entirely dis- 

 proved, and we have discovered an internal mechanism by means of which the 

 equality of the sexes where equality exists is attained. We see how the results 

 are automatically reached even if we can not entirely understand the details of 

 the process." 



The logic of chance in problems of genetics, A. S. Dewing {Anier. Nat., ///f 

 {1910), No. 525, pp. 567-571). — The word "chance" has so many different 

 meanings in biological literature that the author presents a formula by which a 

 definite usage of the term " chance " may be established. 



" In problems of genetics the occurrence of an event said to be due to chance 

 may be ascribed to two separate but independent sets of conditions. The inter- 

 nal conditions are those which are entirely confined to the original universe of 

 discourse of the problem — as for instance, the conditions of the gametes in the 

 chance union of a Mendelian hybrid. The external conditions are those which 

 are not centered in the immediate elements. They are such as age, strength, 

 and the like, of the gamete producing animals. Let cp represent the chance 

 occurrence of any event, and let a, I), c, . . . represent a series of internal con- 

 ditions either known or unknown, and let the coefficients A, B, C, , . ., etc., 

 represent the intensive value of a, h, c in determining the result. Similarly let 

 m, n, o represent certain external conditions and M, N, O their coefficient of 

 intensive value. Then the formula for the chance occurrence, 4>. of an event 

 becomes (p=f (Aa, B?>, Cc, . . . Mm, Nn, Oo . . .)." 



The application of this formula in three different uses of the term in genetics 

 is illustrated by examples. 



DAIRY FAEMING— DAIRYING. 



The bacteriology of commercially pasteurized and raw market milk, S. H. 

 Ayers and W. T. Johnson, .Jr. {U. 8. Dept. Agr./Bur. Aniiii. Indus. Bui. 126, 

 pp. 98, figs. 16). — A study of the bacterial flora of commercially pasteurized 

 and raw milk. Both kinds of milk were examined when fresh and on each 

 succeeding day, as long as the milk was fit for consumption, in order to study 

 the rise and fall of the various groups of bacteria. 



Experiments were made with milk by the " flash " and " holder " methods of 

 pasteurizing in the laboratory, where the process could be controlled. Raw 

 milk high in bacteria as it was produced for butter making was heated in a 

 small pasteurizer of the " flash " type for from 30 to 40 seconds at different 

 temperatures and then cooled. The bacterial production varied at the same 

 temperature with different samples, due it is thought, not to careless methods 

 of controlling the temperature or to contamination, but to the varying propor- 

 tion of heat-resisting species of bacteria or to bacteria in the spore form. When 

 held at 10° C. the proi)ortion of peptonizing bacteria was very low for from 

 3 to 4 days. Held at room temperatures, 22 to 25°, the raw milk in one series 

 remained sweet until the second day. The pasteurized milk soured with normal 

 acid curds on the third day. In the second series, where the counts were all 



