Labile Genes. — Genes which are constantly mutating. 



Lactoflavine. — Part of the vitamin B^ complex. 



Lagging. — Delay in moving from the equator to the poles 

 at anaphase, of one or more chromosomes so that these be- 

 come excluded from the daughter nuclei. 



Lamarckism. — The theory that evolution is brought about 

 by the inheritance of acquired characters. 



"Lampbrush" Chromosomes. — A type of chromosome ap- 

 pearing during the prolonged pachytene stage which occurs 

 in certain yolky eggs. Each chromosome comprises two greatly 

 enlarged chromatids whose chromomeres give rise to looped 

 filaments, 



Lanthanin. — A vague term designating one or more particu- 

 lar structural components of the nucleus; linin. 



Lata-type. — A mutant individual possessing one or more 

 supernumerary chromosomes in its nuclei. 



Latent. — Used of characters whose genes exist in the germ- 

 plasm of an individual without being phenotypically evident. 



Lateral Gynandromorph. — An individual, half of whose 

 body is male and the other half female. 



Lateral Trabant. — See under Trabant. 



Layering. — A method of vegetative propagation which con- 

 sists in bending a branch over, so that part of it can be 

 covered with earth to encourage adventitious rooting. 



Leptonema. — The long, fine, single, unpaired chromosome 

 thread at the leptotene stage (beginning of prophase) of 

 meiosis. 



Leptotene. — An early stage of the prophase of meiosis when 

 the chromosomes are in the form of single fine threads. 



Lethal Factors. — Genes which, in the homozygous state, 

 have such a marked deleterious effect that such homozygous 

 organisms are inviable. Where the homozygote is capable 

 of survival but with impaired efficiency the factors responsible 

 are termed Semi-Lethal. 



"Limited" Chromosomes. — Chromosomes which occur only 



