Yarovization. — Vernalization; the treatment of seeds, before 

 sowing, by any technique designed to hasten the onset of the 

 flowering period of the plants to which the seeds give rise. 



Y-chromosome. — The sex chromosome which is paired with 

 a dissimilar partner in one sex (the heterozygous sex), and 

 which is absent in the other sex (the homozygous sex). See 

 X-chromosome. 



Yolk Nucleus. — Vitelline body; a cytoplasmic body in the 

 young oocyte, which serves as a centre for the yolk-formation 

 in many forms. In many cases it is traceable to the idiozome 

 and its associated structures (Carus; Wilson). 



