CENTROSOMES AND CENTROMERES 



535 



1 ABLE 74 



Abnormal Spindles 



Organism 



Tripolar. 



Vicia Faba 

 Epilobium 

 Melandrium 

 Psilotum nudum 



Author 



Sakamiira, 1920. 

 Michaelis, 1926. 

 Heitz, 1925. 

 Okabe, 1929. 



Tri- and Quadripolar. 



Boveri, 1907 et al. 



Echinoderms 

 Triton 



Anas-Cairina 



Drosophila 



pseudo-obscura. 



Unipolar. 

 Sciara 



Urechis 



A nas-Cairina 

 hybrid. 



Fankhauser, 1934 a 



Crew and Keller, 

 1936. 



Dobzhansky, 1934. 



Metz, 1933. 



Belar and Huth, 



1933- 

 Crew and Roller, 

 1936. 



Stage 



Treatment or Condition 



p.m.c. 

 p.m.c. 

 p.m.c. 

 Spore m.c. 



Cleavage mitosis. 

 Cleavage mitosis. 



Exceptional 



double nuclei 



at meiosis. 

 Poly mitosis. 



M I spermatocyte. 

 First cleavage. 

 Meiosis. 



Spindles without Nuclei (and vice versa). 



Triton 



Fankhauser, 

 a and b. 



1934 



Cleavage 

 sions. 



divi- 



Chloral hydrate. 

 Cold. 

 Natural. 



Usual habit of ^x 

 race. 



Induced 

 dispermy. 



Fertilised egg 



fragments 

 (centrosomes 

 divide out of 

 step) . 



Abnormal hybrid. 



Abnormal hybrid. 



Normal habit (no 



pairing). 

 Not stated. 



Exceptional. 



Fertilised 

 fragments. 



in the protozoan Acanthocystis bodies are present, having the appear- 

 ance of centrosomes, but no evident connection with spindle forma- 

 tion (Belar, 1926 h). It therefore seems that the function of the 

 centrosomes in controlling spindle-formation may be transferred to 

 some other cell-organ, perhaps to an organ which lacks the property 

 of self-propagation that is characteristic of the centrosome. How 

 this may happen will be seen later. 



ih) The Centromeres. The existence of a characteristic body form- 



