1916] ANIMAL PRODUCTION. 867 



" Recent results complete the parallelism between factor groups and chro- 

 mosomes in Drosophila. This strengthens the evidence that separation of 

 linlied factors is due to an interchange between chromosomes. 



" The chief gaps in the information regarding the total frequency of inter- 

 change in the different groups have been filled, and it is found that the usual 

 total frequencies of separation corresi;)ond to the lengths of the chromosomes. 

 This constitutes specific evidence that crossing-over is the method of inter- 

 change between the chromosomes, and that the frequency of crossing-over be- 

 tween factors is determined by their distance apart in the chromosome. It sup- 

 plements the other evidence for these conclusions that had previously been found 

 by Sturtevant in the linear manner of linkage of the factors. 



" It seems uncertain whether crossing-over occurs in the strepsinema stage, as 

 concluded by Jansseus, or earlier in synapsis. The cytological evidence at 

 present at hand would seem insufficient to settle this point. Possible tests for 

 various alternative mechanisms of crossing-over are proposed. 



" In order to study the nature of crossing-over by means of ' interference ' 

 stocks were made up that differed in regard to many factors. Females hetero- 

 zygous for 22 pairs of factors were thus obtained, and a special method was 

 devised for testing their output. Other special methods for obtaining multiple 

 stocks and for eliminating discrepancies due to differential viability have also 

 been presented. The results have been arranged in the form of a curve showing 

 the amount of interference for various distances. The results thus far obtained 

 confirm those obtained by less exact methods, and also give evidence that in- 

 terference decreases gradually with distance from a point of crossing-over; this, 

 taken together with certain evidence from nondisjunction, lends some probability 

 to the view that crossing-over occurs at an early stage in synapsis. 

 " A case of crossing-over in an embryonic cell of a male is reported. 

 " Incidentally, the experiments have afforded an extensive test of Castle's 

 assumption of contamination of factors by their allelomorphs. Outcrossing in 

 each generation for 75 generations has failed to change any of the factors." 

 A bibliography of references is included. 



Investigation in Mendelian inheritance, G. Lefe\tie and E. H. Ruckeb 

 (Missouri Sta. Bui. 141 (1916), p. Jf2).—A progress report of work in crossing 

 Silver-Spangled Hamburg X Brown Leghorn, and Sebright X Rose-Comb Black 

 Bantam. In the latter cross the Fi cocks showed three conditions: (1) Male- 

 feathered (SS) ; (2) hen-feathered (ss) ; and (3) intermediate condition (Ss). 

 Total, digestible, and manurial composition and compensation value of 

 foodstuffs, compiled by G. S. Robertson (Chelmsford, England: East Anglian 

 Inst. Agr. [1916], pp. 25).— Compiled analyses are given of a large number of 

 feeding stuffs and similar materials. 



Studies on the mineral elements in animal nutrition, E. B. Forbes (Jour. 

 Wash. Acad. Sci., 6 (1916), No. 13, pp. 4SI-U6) .—The author summarizes the 

 results of metabolism experiments conducted at the Ohio Experiment Station 

 and previously reported from various sources. 



Inspection of feeding stuffs (Xeio York State Sta. Bui. 420 (1916), pp. 161- 

 309). —Analyses of the follo%\ing feeding stuffs are given: Cotton-seed meal; 

 linseed meal ; malt sprouts ; distillers' and brewers' dried grains ; yeast or vine- 

 gar dried grains ; corn gluten feed and meal ; hominy feed ; meat scrap and beef 

 scrap ; fish scrap ; tankage ; bone meal ; red dog flour ; wheat bran and middlings ; 

 rye bran and middlings; buckwheat bran and middlings; barley middlings; 

 corn, pea, coconut, and alfalfa meals, corn oil cake meal, and peanut oil meal ; 

 dried beet pulp ; oat hulls ; and various mixed and proprietary feeds. 



The grazing industry of the blue grass region, L. Gabbier (U. S. Dept. Agr. 

 Bui 391 (1916), pp. 18, figs. i6).-This bulletin gives a general review of the 



