ANIMAL PKODUCTION. 67 



56, 57). — The difBciilties in the way of accepting the nnclens as bearing the 

 chief rOle in inheritance are indicated. 



Tetraplasy, the law of the four inseparable factors of evolution, 11. F. 

 OsBORN (Jour. Acad. Nat. Sci. Phila., 2. ser., 15 {1912), pp.* 273-309).— A sum- 

 mary and explanation of various biological principles which the author has 

 previously discussed, especially the influence of environment, ontogeny, 

 heredity, and selection on the evolution of plants and animals. See also a 

 previous note (E. S. R., 27, p. 369). A bibliography is appended. 



Concerning the problem of the carriers of heredity, F. Vejdovsky {Zum 

 ProUem der V ererhungstrager. Prague, 1912, pp. 184, P^s. 12, figs. 16; rev. in 

 Arch. Mikros. Anat., SO {1912), No. 3, 11, pp. 124, 125). —A study of the finer 

 structure of chromosomes and other cell structures in several species of in- 

 vertebrates, with special reference to the transmission of the hereditary mate- 

 rial from one generation to another. The mitochondria are not considered by 

 the author as taking part in the process of inheritance. A bibliography of about 

 450 titles is appended. 



Mendelism and interspecific hybrids, O. F. Cook {Amer. Nat., 47 {1913), 

 No. 556, pp. 239-245). — A discussion of the significance of alternative inheritance 

 for the practical breeder. It is pointed out that the data on crosses of zebus 

 and cattle, in an article previously noted (E. S. R., 28, p. 68), furnish a better 

 illustration of the coherence of characters derived from the same parental stock 

 than of a Mendelian freedom of combination of the contrasted characters. A 

 comparison is made of these crosses with results obtained with cotton (E. S. R., 

 21, p. 40; 22, p. 37). 



" The practical question to be determined is whether the Durham-like and 

 Brahma-like individuals of the second and later generations are equal to the 

 original parental varieties, and whether the intermediate individuals maintain 

 the average of the first generation. ... To increase the pure stock of Brahma 

 cattle, and thus increase the possibilities of producing first generation hybrids, 

 may be more important than the breeding of hybrid varieties. At least this 

 is the suggestion to be drawn from the failure of many attempts to develop 

 superior useful varieties of cotton and other seed-propagated plants from Inter- 

 specific hybrids. As a barrier to a permanent union of two species degenera- 

 tion in the second or later generations of a hybrid stock may be as effective as 

 sterility in the first generation. It may prove very fortunate that Mr. Borden 

 has imported Brahma cows as well as bulls, for this may make it possible to 

 perpetuate the Indian breeds in Texas. 



"A tendency to deterioration in the later generations of hybrids is likely to 

 be marked as long as hybrids are crossed back on one of the parental stocks, 

 instead of being bred with each other. This is because even dilute hybrids 

 share some of the stimulation effect shown in the first generation. But these 

 questions of vigor and fertility, though of fundamental importance in practical 

 breeding, lie outside of the range of the Mendelian theory." 



A simple test of the goodness of fit of Mendelian ratios, J. A. Harris 

 {Amer. Nat., 46 {1912), No. 552, pp. 741-745).— It is pointed out that the prob- 

 able error between the observed and calculated results in breeding experi- 

 ments must be judged by something more than an empirical inspection or by 

 the method of Johannsei ", except for the simple 3 : 1 ratios. By applying the 

 formula furnished by Pearson *, and using Elderton's " tables, the author has 

 suggested a comparatively simple and reliable method for determining the 



" Elemente der Exakten Erblichkeitslehre, pp. 402-410. 

 " Phil. Mag. and Jonr. Sci., 50 (1900), pp. 157-175. 

 <^ Biomotrika, 1 (1901), pp. 155-163. 



