1920] ANIMAL, PRODUCTION. 269 



average of the two limiting values was found to give a good fit to the published 

 data of Morgan and Bridges, but no theoretical significance is claimed for this 

 result. 



The author proposes that the unit of distance defined by his equations be 

 termed a " morgan." When the distance is sniull the percentage of cros.sovers 

 gives approximately the number of ceiitimorgans. 



Chiasmatype and crossing over, K. li. Wilson and T. H. Morgan {Amer. 

 Nat., 5.'t (1920), No. 632, pp. 193-219, figs. 8).— Each author discusses this topic 

 independently, Wilson from the* standpoint of a cytologist and Morgan from 

 that of an experimental geneticist. Wilson points out that genetical speculation 

 as to the mechanism of crossing over has outstripped cytological investigation 

 of the behavior of chromosomes at synapsis, but he records his belief that the 

 explanation of crossing over lies in^some form of torsion of the chromosomes, 

 though perhaps not in the original chiasmatype hypothesis. 



Spermatogenesis of the dog, J. Y. Malone {Trans. Amcr. Micr-os. Soc, ST 

 (191S), No. 2, pp. 97-110, pis. 2). — The diploid number of chromosomes in. the 

 male dog was found to be 21. The unpaired chromosome (X-element or sex 

 chromosome) passes undivided to one pole at the first spermatocyte (reduction) 

 division. 



It is stated that the mature spermatozoa could be separated into two distinct 

 classes on the basis of size. 



Experimental degeneration in the testis of the dog, A. Kuntz {Anat. Rec, 

 n U919), No. .',, pp. 221-28Jf, figs. 4).— The author reports a study of the de- 

 generative changes in the seminal epithelium in the testes of two groups of dogs. 



In dogs subjected to an operation in which the sympathetic nerve supply to 

 the testes was eliminated the spermatocytes and spermatids became necrotic 

 and gradually sloughed away. This degeneration resembled that produced by 

 exposure to X-rays and also the condition described by Allen (E. S. R., 42, 

 p. 468) in rats fed on a diet deficient in water-soluble vitamin. Ligature and 

 resection of the right ductus deferens produced a somewhat similar degenera- 

 tion, but was characterized by a much more pronounced sloughing of the 

 tissue. The interstitial tissue in both cases showed marked hypertrophy. 



Notes on wool in India, A. H. Silver and J. K. Mehta {Calcutta: Indian 

 Munitions Bd., 1919, pp. l5]-\-89). — The authors di.scu.ss sheep breeding in 

 India and the Indian wool trade, and present comprehensive statistics of wool 

 production, imports and exports, prices, and woolen manufactures. 



Stallion enrollment. — VIII [i. e. IX], Report of stallion enrollment work 

 for the year 1919 with lists of stallions and jacks enrolled, H. E. McCart- 

 ney {Indiana Sta. Ciro. 94 {1919), pp. 92, fig. i).— This report of the Stallion 

 Enrollment Board consists mainly of a directory of enrollments and renewals 

 for the calendar year of 1919, classified by counties. During the year there 

 were enrolled 1,922 pure-bred stallions, 889 grade and scrub stallions, 787 

 registered jacks, and 390 grade and scrub jacks. With the exception of the 

 registered jacks these totals are all lower than in 1918 (E. S. R., 41, p. 178), 

 but the proportion of pure-bred stallions is higher. 



Feeding for egg production: Vegetable v. animal protein in egg produc- 

 tion, P. Moore {Idaho Sta. Bui. Ill {1919), pp. 11, fig. i).— The plan and the 

 first year's results of this investigation have been noted from a preliminary 

 report ft^. S. R., 40, p. 670). The plan was changed March 1 of the third year 

 (1918) and the experiment terminated the following summer because the supply 

 of shorts was exhausted. 



The production data cited consist of the relative egg records of the pens 

 each year and the proportions of heavy and light eggs laid in the different 



