Archiplasm — 13 — Autoauxone 



at one time to denote any star-like group of chromosomes at 

 mitosis. 



Astrocentre. — The centrosome; the self propagating activity- 

 centre in cell division in most animal cells and in the 

 Thallophyta. 



Astrosphere. — A collective term for the centrosome together 

 with the surrounding aster zone; centrosphere ; attraction 

 sphere. 



Asynapsis. — Asyndesis, q.v. 



Asynaptic. — Asyndetic. See Asyndesis. 



Asyndesis. — Absence of the fusion of homologous chromo- 

 somes during meiosis. Adj. Asyndetic. 



Asyndetic. — See Asyndesis. 



Asyngamic. — Unable to cross by reason of differences in 

 time of flowering. 



Atavism. — The reappearance of a character after a lapse 

 of one or more generations, due to the character being reces- 

 sive or being dependent on complementary factors, or as a re- 

 sult of back-mutation. Atavism is sometimes called "throwing 

 back" (to an ancestor) and the aberrant individual is termed 

 a "throw-back". 



Atelomitic. — Applied to chromosomes with non-terminal 

 spindle attachments. 



Attached X-chromosomes. — X-chromosomes which are at- 

 tached to each other at their centromere ends. 



Attachment Chromomere. — The attachment particle or 

 centrogene as distinct from the attachment region or centro- 

 mere. 



Attachment Constriction. — Centromere; spindle attachment; 

 insertion region; kinetochore; a non-staining localized region 

 in each chromosome which remains single for some time after 

 the rest of the chromosome has divided and which appears to 

 be 'attached' to the spindle 'fibre'. 



Attachment Region. — Attachment Constriction q.v. 



Attraction Particle. — A central granule in the centrosome; 

 centriole. 



Attraction Sphere. — Astrosphere; centrosphere; a collective 

 term for the centrosome together with the surrounding aster 

 zone. 



Attraction Spindle. — The terminal portions of the spindle. 



Auto-alloploid. — An organism which has originated by a 

 doubling of the chromosome complement of an allotetraploid. 



Autoauxone. Any substance which is biologically highly 



active and which is synthesized by the organism itsfelf. 



