Knight — 118 — Dictionary 



Polygenesis. — The production of a new type at more than 

 one place or more than one time. 



Polygenic Balance. — The harmonious balance, between the 

 systems of polygenes in a species and the natural environment 

 of that species built up as a result of natural selection and 

 enabling the organisms to develop normally and competitively. 



Polygenic Character. — A character whose inheritance is con- 

 trolled by many genes each having an effect which is small 

 compared with non-heritable variation (Mather). 



Polygenist. — One who believes in the multiple genesis of 

 man. cf. Monogenist. 



Polygenom Hybrid. — A hybrid whose somatic nuclei carry 

 more than two complete genoms comprising the genoms of two 

 or more distinct species. 



Polygoneutic. — Producing several broods per season. 



Polygynous. — (i) Having numerous styles, (ii) Having more 

 than one female mate at a time. N. Polygyny. 



Polyhaploid. — An organism formed by a halving of the 

 chromosome number of a polyploid. 



Polyhybrid. — An individual heterozygous for several genes. 

 A hybrid produced by crossing two individuals differing in 

 several genes. 



Polykaryotic. — Polycaryotic, q.v. 



Polymeric Genes. — Non-allelomorphic genes governing the 

 same character and having a similar effect on it. 



Polymorphism. — The occurrence together in the same habitat 

 of two or more forms of a species in such proportions that the 

 rarest of them cannot be maintained by recurrent mutation 

 (Ford), If the proportion of one of these forms is increasing 

 in the population, the phenomenon is called Transient Poly- 

 morphism, whereas a form which is maintained in a constant 

 proportion by a balance of selective agencies exemplifies Bal- 

 anced Polymorphism. 



Polymorphism, Neutral. — Polymorphism which is dependent 

 on the action of alleles which are approximately neutral as 

 regards their survival value. 



Polymorphism, Regional. — The existence of two or more 

 distinct forms of a species which are located in different 

 regions; geographic polymorphism. 



Polynucleate. — Having several nuclei. 



Polyoestrus. — Having a recurrent cycle of oestrus periods 

 in the one sexual season. 



Polypetalous. — Having several distinct (separate) petals. 



