APPENDIX I 



Chiasma Theory of Pairing, that whenever two chromosomes which 

 have been paired at pachytene remain associated until metaphase, 

 they do so by virtue of the formation of one or more chiasmata. 

 Does not apply to the heterogametic sex in certain animals. 

 Darlington 1929. 



Chiasmatype Theory, that only sister chromatids are associated after 

 chiasma formation and that every chiasma therefore results from 

 crossing-over between two chromatids. Darlington 1930. Derived 

 from Janssens' (1909) tlieory that crossing-over and chiasmata were 

 causally related in various ways. 



CfflMAERA, a plant composed of tissues of two or more genetically distinct 

 types, as a result of mutation, irregular mitosis, plastid segregation, 

 or artificial fusion by grafting. Divisible into two kinds. Banr 

 1909:— 



Periclinal, in which the distinct tissues are arranged in concentric 

 layers. 



Sectorial, in which the distinct tissues are arranged in cross-sections 

 as sectors of a circle. 



A compound Sectorial-Periclinal is also termed MEmcuNAL. j0rgenst'n 

 1928. 



Chondriosomes, bodies in the cytoplasm wliich are beheved to be self- 

 propagating, including Mitochondria and Golgi-Bodies. Bcnda 

 1904. 

 Chromatid, a half chromosome between early prophase and metaphase 

 of mitosis, and between diplotene and second metaphase of meiosis. 

 After these stages, i.e. during anaphase, it is called a Daughter 

 Chromosome. The separating chromosomes at first meiotic anaphase 

 are known as daughter-bivalents, or, if single chromatids derived 

 from the division of univalents, daughter-univalents. McClung 1900. 



Chromatid Bridge, a dicentric chromatid with centromeres passing 

 to opposite poles at anaphase. S. G. Smith 1935. 



Loop Chromatid, a chromosome arm whose chromatids show sister- 

 reunion V. X-ray. 



Sister Chromatids, those derived from division of one and the 

 same chromosome, as opposed to non-sister chromatids which are 

 derived from partner chromosomes at pachytene, or from any 

 distinct pair of chromosomes at mitosis. Sister Strands of Bridges 

 and Anderson 1925. 



Chromatin, Chromosome Thread to* wliich nucleic acid is attached. 

 Fleming 1879, Boveri 1904. 



382 



