APPENDIX I 



Mean (continued) 



Working Mean, a value approximating to the mean used for the 

 purpose of hghtening the calculations of the mean, the sum of 

 squares and other quantities. 



Median, the value of a variate on each side of which He equal numbers 

 of observations. 



Megaspore, a spore which develops into a gametophyte bearing only 

 female gametes, as opposed to Microspore. 



Meiosis, a double Mitosis in which the nucleus divides twice but the 

 chromosome only once. The prophase of meiosis is the prophase 

 of the first of the two divisions, v. Mother Cell. Farmer and Moore 

 1905. 



Mendel's Laws of Inheritance, i. The Law of Segregation, that the 

 gametes produced by a hybrid or heterozygote contain unchanged 

 either one or the other of any two factors determining alternative 

 unit characters in respect of which its parental gametes differed. 

 2. The Law of Recombination, that the factors determining different 

 unit characters are recombined at random in the gametes of an 

 individual heterozygous in respect to these factors. Mendel 1865. 



Merogony, development of part of an egg with the sperm nucleus, but 

 without the egg nucleus. Genetically equivalent to Male Partheno- 

 genesis. Delage 1899. 



Metabolic Stage, Resting Stage. 



Metaphase, the stage of mitosis or meiosis at which the undivided 

 centromeres of the chromosomes lie on the spindle. Strasburger 

 1884. 

 Metaphase Plate, the group of chromosomes arranged in the equatorial 

 plane of the spindle. 



Metaxenia, v. Xenia. 



Microchromosomes, small chromosomes which pair at meiosis only 

 at metaphase and therefore without chiasma formation (in the 

 Hemiptera-Heteroptera). Wilson 1905. 



Micronucleus. I. The small permanent reproductive nucleus of the 

 Infusoria, as opposed to the short-hved multiple Macronucleus. 

 2. A nucleus separate from the main nucleus formed at telophase by 

 one or more lagging chromosomes or fragments. 



Microsome, largely submicroscopic particles in the cytoplasm charac- 

 terized by the presence of ribose Nucleic Acid and phosphohpids. 

 Claude 1943. 



Microspore, a spore which develops into a gametophyte bearing only 

 male gametes, as opposed to Megaspore. v. PoUen Grain. 



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