M I, M II. — The first and second metaphases respectively, 

 in meiosis. 



Macrandrous. — Having unusually large male organs. 



Macroconjugant. — Macrogamete, q.v. 



Macro-evolution. — (i) The evolutionary process as con- 

 sidered over long periods of time and large 'groups' of or- 

 ganisms, (ii) Goldschmidt's term for the large-scale evolu- 

 tion which is supposed to give rise to new species and genera 

 by means of 'systemic mutations' which involve a radical 

 change in the primary chromosomal pattern or reaction sys- 

 tem, cf. Micro-evolution. 



Macrogamete. — The bigger of two conjugating gametes 

 (typically the female). 



Macro-mutation. — A 'mutation* bringing about a simul- 

 taneous change in a number of different characters. 



Macront. — A mother-cell which gives rise to macrogametes. 



Macronucleus. — The larger of the two nuclei in the In- 

 fusoria; the "vegetative" nucleus. 



Macrosomes. — Alveolar spheres which occur in alveolar 

 protoplasm. 



Macro-pyrenic. — (i) Having nuclei which are considerably 

 larger than the average for the species, individual, etc. (ii) 

 An individual of this type. 



Macrospecies. — Large species typically having considerable 

 variability but well differentiated from other related species. 



Macrospore. — Megaspore, q.v. 



Maiosis. — Meiosis, q.v. 



Male Haploidy. — A system of sex-determination in which 

 the haploid individuals are males whilst the diploid condition 

 determines femaleness. 



Male-limited Chromosomes. — Chromosomes which occur 

 only in nuclei of the male germ-line, never in somatic nuclei 

 of either sex, and never in nuclei of the female germ-line; 

 androsomes. 



Male Parthenogenesis. — The development of an individual 

 from a male gamete without fertilization having taken place. 



