APPENDIX I 



MiSDivisiON, spontaneous crosswise (instead of lengthwise) division of the 

 centromere on the spindle especially of univalents at M I and daughter 

 univalents at M II. v. Telocentric. Darliuqton 1939. 



Mitochondria, v. Chondriosomes. Beiida 1897. 



Mitosis, the process by which division of the nucleus is accompUshed 

 by that of its constituent chromosomes and usually accompanied 

 by that of its containing cell. Flcmming 1882. 



MixoPLOiD, a diploid-polyploid Chimaera. Nemec 1910. 



Mode, the value of a variate shown by the class most frequently observed. 



MoDincATiON, a non-heritable change (caused by difference in the 

 environment), v. Dauermodification. Baur 1911. 



Modifying Gene, Modifier, a gene whose differences are revealed by 

 their effects on the expression of another gene. v. Polygene. 



Monoecy, in plants the condition in which male and female gametes are 

 borne by different flowers of the same individual, v. Dioecy. 



Monogenic, of an hereditary difference determined by one gene differ- 

 ence as opposed to two (Digenic), three (Trigenic) or many (Poly- 

 genic). 



Monohybrid, heterozygote in respect of one gene. 



Monoploid, having the Basic Number of chromosomes. 



Monosomic, an otherwise diploid organism lacking one chromosome 

 of its proper complement {ix — i). v. also Polysomic. Blakeslee 1921. 



Monozygotic, derived from one fertilized egg (of Twins or multiplets 

 then called Identical). 



Morphogenesis, the differentiation of structures during development. 



Mosaic, i. In animals, the equivalent of a Chimaera. 



2. In plants a Chimaera produced by recurrent mutation. 



3 . A Virus disease producing the appearance of a mosaic in plants. 

 Mother Cell, a cell with a diploid nucleus which, by meiosis, gives 



four haploid nuclei, e.g. the spore mother-cell in Bryophyta and 

 Pteridophyta, the Microspore or Pollen mother-cell and the Mega- 

 spore or Embryo-Sac mother-cell in Flowering Plants. In animals 

 the sperm mother-cell is known as the Spermatocyte and the egg 

 mother-cell as the Oocyte. 



MuLTiNOMiNAL Series, the series obtained by expanding, to any power, 

 the sum of three or more quantities (a + b + c . . .)°. 



Multiple Allelomorph, v. Allelomorph. 



Multiple Chromosome, the product of fusion of two chromosomes. 

 McClung 191 J. 



Multiple Factors, Polymeric Genes. 



Multivalent, v. Univalent. 



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