Knight — 108 — Dictionary 



to members of a pair in meiosis (co-orientation) (Darling- 

 ton). 



Ornithophilous. — Pollinated by means of birds. 



Orthogamy. — The normal relations of male and female (Car- 

 penter). 



Orthogenesis. — Purposive, 'predetermined' evolution towards 

 a definite objective. A tendency to vary continuously in the 

 same direction. 



Orthoploid. — A polyploid with a balanced number of complete 

 chromosome sets. cf. Aneuploid. 



Orthoselection. — Selection which increases the likelihood of 

 the continuance of any particular adaptive trend. Selection 

 acting over a long period of time with a general trend in one 

 particular direction. 



Orthospiral. — A spiralization of such a type that no secondary 

 compensational twisting occurs in the fabric of the thread. 

 cf. Anorthospiral. 



Outcross. — A cross (generally resulting from natural pollina- 

 tion) to an individual of a different strain, variety or type. 



Ovariectomy. — The surgical removal of an ovary or ovaries. 



Ovary. — The part of the flower which contains the ovules ; the 

 immature fruit. In animals, a female gonad or reproductive 

 gland. 



Overstepping. — This occurs when an animal, during its own 

 ontogeny, passes through the ontogenetic stages of its ancestor 

 but beyond the final adult stage of that ancestor; hypermor- 

 phosis. cf, Anaboly. 



Ovogenesis. — Oogenesis, q.v. 



Ovotestis. — A gonad which is composed, in part, of testicular 

 substance and, in part, of ovarian tissue. 



Ovule. — A body containing a female gamete and which, after 

 fertilization, develops into a seed. 



Ovum. — The female gamete or egg. PI. Ova. 



Oxychromatin. — (i) Linin, q.v. (ii) That part of the nucleus 

 which stains readily with acid dyes. 



Oxyphilic. — Staining readily with acidic dyes. 



