ANIMAL PRODUCTION. 469 



ANIMAL PRODUCTION. 



Some recent studies on growth, li. Pkarl (Amcr, Nat., ^3 (1909), No. 509, 

 pp. .iO.i-.ih}). — This is a discussion on the application of quantitative methods 

 in studies of growth changes. 



The recent work reviewetl includes that of Donaldson on rats and man, Kel- 

 licott on dogfish, Burnett on breaking strength of bones in pigs (E. S. R., 20, p. 

 868), and Armsby on meat production (E. S. R., 20, p. 605). Robertson's work 

 on normal rate of growth is also discussed, and it is pointed out that the theo- 

 retical curves used by Rol)ertson when fitted to observational data give an 

 uneven and biased distribution of errors, and that similarity of quantitative 

 r(>lations between phenomena can not safely be taken as proof of qualitative 

 identity. The final proof of qualitative identity of phenomena must always in 

 the last analyses be qualitative in its nature. 



The capacity of animals to grow under adverse conditions, H. J. Waters 

 {Proc. Sot: I'roiit. Ayr. t^cL, 29 (1908), pp. 71-96, figs. 5, charts 3).— Data are 

 reported on changes in body conformation of steers when kept on maintenance 

 and submaiutenance rations. 



It was found that bones may lengthen and fat be resorbed when the weight 

 remains stationary. An examination of fat cells showed them to be reduced 

 in size. Three steers, 9, 16, and 17 months old, respectively, when kept on a 

 maintenance ration for a year remained practically stationary in weight but 

 increased on an average 5.91 cm. in length of head, S.75 cm. in height at the 

 withers, and 3.16 cm. in depth of chest. The same steers decreased on an 

 average 4.66 cm. in width of chest. Full-fed steers were found to increase in 

 height more rapidly than those on a maintenance ration. Animals kept on a 

 submaiutenance ration increased in height at withers and length of head, but 

 at the same time lost in weight. Chemical analyses showed a decline in per- 

 centage of fat and an increase in percentage of water and protein in animals 

 kept on maintenance and on submaiutenance rations. 



Heredity, variation, and evolution in protozoa, I, H. S. Jennings (Jour, 

 Expt. Zoo}., (1908), No. .'/, pp. 577-632, figs. 22).— This is a study of the 

 inheritance of new characters and mutilations in Paramecium. 



The couclusions reached are that in protozoa as in metazoa the inheritance 

 of acquired characters meets the same difficulty and does not occur more readily 

 in the one group than in the other, although it has been commonly a.ssumed 

 that in protozoa the parent and progeny are practically identical, hence that 

 any new or acquired characters will be inherited. There was one doubtful 

 case, however, in which certain individuals of one race tended to remain united 

 after fission. 



The problem of inheritance lies not in the separation of soma and germ but 

 .in the process of cell division. Before a new character can be inherited it 

 must be the result of such a modification of the ])arent cell as will cause a 

 change in tlie proces,ses of i-eproduction, and this is eciually true of metazoa 

 and protozoa. 



Heredity, variation, and evolution in protozoa, II, H. S. Jennings (Proc. 

 Amcr. Phil. ,Soc., .',7 (1908), No. 190, pp. 393-5Ji3, figs. 7, dgms. 6'),— This paper 

 deals with heredity and variation in size and form in Paramecium, with 

 studies of growth, environmental action, and selection. 



The author shows by polygons of variation and by correlation tables that 

 as in higher organisms the Paramecia were made up of numerous races. The 

 individuals of a race varietl much among themselves, but these variations were 

 matters of growth and environment and were not inherited. Selection had no 

 effect within a pure line. The size was determined by the line to which the 



