ANIMAL PRODUCTION". 273 



" If the thread be merely smeared with a soap of the base, even in the presence 

 of considerable excess of fatty acid, the same resnlt is achieved; the effect is 

 therefore due to soap formation and not to hydroxyl ions. 



" The mechanical division of the droplets is brought about by violent stream- 

 ing movements from the equator of the drop toward the poles, due to the lower- 

 ing of the surface tension in the equatorial region brought about by the soap. 

 It is pointed out that these facts confirm Loeb's hypothesis that cell division is 

 bi'ought about through the mechanical agency of streaming phenomena. 



" It is suggested that the equatorial lowering of surface tension and conse- 

 quent streaming phenomena which lead to cell division are brought about by 

 cholin or soaps of cholin liberated in the cell through the splitting of lecithin 

 in nuclein synthesis." 



Recent work on the determination of sex, L. Doncaster (8ci. Prog. Twen- 

 tieth Cent., Jf (1909), No. 13, pp. 90-10J,).—A sketch of recent work on the 

 evidence concerning the presence of a sex determinant in the germ cells com- 

 l)arable in nature with the Mendelian unit, from which the author concludes 

 " that the probabilities are overw^helmingly in favor of the idea that the de- 

 termination of sex is not consequent on the accidental preponderance of one 

 or other of two nicely balanced tendencies, but is due to fixed and unalterable 

 characters inherent in the germ cells." There are numerous references to the 

 literature on the subject. 



The making- of species, D. Dewak and F. Finn {London and New York, 

 J 909, pp. XlX+JfOO, pis. 16). — This book attempts to present in simple language 

 biological problems such as the natural selection theory, hybridism, fertility of 

 hybrids, jNIendeliau inheritance, and other factors concerned in the evolution 

 of species in nature and under the influence of man. Throughout the book 

 there is a strong protest against the views of the post-Darwinians. It is 

 lK)inted out that bionomics, or the science of living animals, occupies too small 

 a place in English scientific literature. In a discussion as to what species will 

 survive in the future, it is stated that the making of species, their survival, 

 and the future of biology lie largely in the hands of the practical breeder. 



On the colors of horses, zebras, and tapirs, II. I. Pocock (Ann. and Mag. 

 Nat. Hist. [London], 8. scr., 4 {1909), No. 23, pp. 40-Mi5).— This contains a dis- 

 cussion of the nomenclature of colors and color patterns in Equidse and other 

 large mammals. Various theories which account for the causation and inherit- 

 ance of albinism, dappling, and the zebroid pattern are reviewed. The author 

 thinks that the Equidje are descended from dark colored animals patterned with 

 white spots, running into longitudinal lines originally and in a late state of evo- 

 lution becoming arranged in transverse bars over the neck and body. If this 

 theory is true, then the white spots of dapple-grey horses represent phylogeneti- 

 cally the white spots of a tapiroid progenitor, a stage antecedent to the vertical 

 zebroid bands hitherto regarded as the most primitive pattern extant in the 

 Equidte. 



The Scandinavian origin of the hornless cattle of the British Isles, J. 

 AViLSON {8ci. Proc. Roy. Dublin Soc., n. ser., 12 {1909), No. 15, pp. 145-164, 

 figs. 6). — It is the purpose of this paper to show that the existing and extinct 

 British breeds of hornless cattle may all be traced back to a Scandinavian origin, 

 which is contrary to the itrevaleut opinion that most of the British hornless 

 breeds of cattle have originated independently. The lines of evidence pi'esented 

 are that these hornless breeds were originally of similar character, and therefore 

 presumably of connnon origin ; that their arrival in the British Islands coincided 

 with that of the Norsemen ; that cattle of similar character were taken to other 

 parts of Europe with which the Norsemen were associated; and that traces at 



