No. 1, Mat, 1921] GENETICS 45 



parents unite in the most intimate manner but without the loss of their individual 

 identity, thus completing the process of union inaugurated by fertilization. — 10. Still, dis- 

 tinguished by characteristics of form, size and behavior, they are then segregated by chance 

 and distributed again into mature germ cells in a simplex series. Through these they may be 

 traced again into another generation of organisms where they repeat the series of processes. — 

 11. Fertilization, although not necessary to reproduction, and omitted in parthenogenesis, is 

 required in biparental inheritance and there serves the essential purpose of introducing the 

 necessary duplicate control factors — the chromosomes. — C. E. Mc Clung. 



293. MacCurdy, M. Conjugation and fission-rate in Arcella vulgaris (Ehrenberg). 

 [Abstract.] Anat. Rec. 20: 199. 1921. — In pedigreed cultures of Arcella vulgaris under lab- 

 oratory conditions the fission rate varies considerably. A general average rate in a non- 

 conjugating line derived from 1 parent cell was 1 division for every 2.56 days. At times when 

 estimated for weekly periods, the fission rate for any one line would increase for a period giv- 

 ing a higher rate and this would be followed by a period of slower divisions. The rate in a 

 parallel line might not be the same. — Conjugation was most often found to occur at times of 

 low fission rate. In many cases this was found to occur at intervals of about a month. There 

 are exceptions. Many ex-conjugants gave a higher rate of division for a period following con- 

 jugation than parallel lines gave for the same period. Some non-conjugants gave a higher 

 rate than some ex-conjugants. Certain nuclear conditions are pointed out and their probable 

 significance considered. — M. MacCurdy. 



294. Macoun, W. T. Apple breeding in Canada. Proc. Amer. Pomol. Soc. 1917: 11-27. 

 1 pL, 1 fig. 1918. [See Bot. Absts. 7, Entry 985.] 



295. Malaquin, A. Reproduction sexuee et reproduction asexuee. [Sexual and asexual 

 reproduction.] Compt. Rend. Acad. Sci. Paris 171: 1403-1406. 1920. 



296. Marchal, E. Recherches sur les variations numeriques des chromosomes dans la 

 serie vegetale. [Studies on the numerical variations of the chromosomes in plants.] Mem. 

 Acad. Roy. Belgique CI. Sci. 4: 1-198. [Year?] 



297. Massart, J. La notion de I'espece en biologic. [The notion of species in biology.] 

 Bull. CI. Sci. Acad. Roy. Belgique 1920:366-381. 4 fig. 1920.— The classic definition of 

 species according to the author, does not correspond to the Linnean species, nor even to the 

 Jordanian species, but to the line. — 'A good example of the line is furnished by Quercus ilex. 

 The nuts of a tree are similar. They often differ from one tree to another, but often a little 

 group has the same type of nuts. Each tree gives every year the same form of nuts. The 

 young plants show that the nuts of a single tree are similar, but they differ from those of 

 another individual. Each tree has in the young stage more spiny leaves. There are 

 many other examples of stable lines in wild species. In the definition of the line, it is neces- 

 sary to include neither self-fertilization nor homozygous. In fact, some self-sterile lines 

 (Lolium perenne), and some heterozygous lines (Prirmda insecta) are known. The taxono- 

 mist and the biogeographer should content themselves provisionally with Linnean and Jor- 

 danian species. The lines have three origins: Hybridization, generative mutation, and vege- 

 tative mutation. — Henri Micheels. (Translated by Geo. H. Skull.) 



298. Mathews, J. Wrenford. Sheep and wool for fanners. Cross-breeding experi- 

 ments. Results of lamb-raising trials. Agric. Gaz. New South Wales 31: 761-770, 846-852. 

 10 fig. 1920. 



299. Meves, Friedrich. Eine neue Stiitze fiir die Plastosomentheorie der Vererbung. 

 [A new support for the plastosome theory of heredity.] Anat. Anzeig. 50 : 551-557. 2 fig. April, 

 1918.— Author offers evidence, based upon studies of fertilization of egg of nematode Ox?/«ris, 

 that plastosomes or "plastochondria" are introduced into egg by spermatozoon; and that 

 they, together with similar bodies from egg, are portioned out to first two daughter cells 

 of zygote, and presumably play a part in heredity as well as the nuclei. — F. B. Sumner. 



