128 MEIOSIS IN DIPLOIDS AND POLYPLOIDS 



Fig. 42. — Multivalent configurations of small chromosomes, seen in 

 side view of first metaphase. Roman numerals show the number 

 of chromosomes in the configurations. Ill a-c, IV a-k, and 

 VI b, c and f, have only terminal chiasmata. The rest have 

 some interstitial chiasmata. IV c has an imperfect quadruple 

 chiasma {cf. Ch. XII), IV d a perfect one. X ca. 6000. 



These figures have been found in Prunus (D., 1928, 1930 a, 

 Meurman, 1929), Pyrus (D. and Moffett, 1930; Moffett, 1931), 

 Solanum (Jorgensen, 1928), Primula (D., 1931 a), Galeopsis 

 (Munt?ing, 1932). and will probably be found in many other 

 genera where they have previously escaped notice. 



chromosomes at metaphase is conditioned by the formation of the 

 chiasmata. 



In triploid Hyacinthus there are three types of chromosomes, long, 

 medium and short, with average frequencies of chiasmata amongst 



