358 



W. J. C. Lawrence 



Cytologia 2, 



9u 





..<^' 



d 



f 



iiir^%0^ 



Fig. 2. 



g 



Fig. 2. Meiosis in £». coceinea (2n=32) 



a. mid-diakinesis. 6. late-diakinesis. c. pro-meta- 

 phase (note association of bivalents). d. late pro- 

 metaphase, orientation on spindle almost complete. 

 e-f. polar views MI. (e= early metaphase). g. side 

 view (complete) MI showing secondary association 

 of bivalents. 



shown in the first column, 

 those loosely associated in 

 the second. The classifi- 

 cation is necessarily arbi- 

 trary with regard to de- 

 ciding where association 

 begins. Considering the 

 results together we find 

 that association occurs be- 

 tween 6 groups of 2 and 2 

 groups of 3 bivalents. 



Anaphase is normal 

 but secondary association 

 is maintained. Inter kine- 

 sis is relatively short and 

 at the 2nd metaphase 

 some of the chromosomes 

 are still associated. Tetrad 

 formation is regular. 



D. coceinea. 



The diploid number of 

 chromosomes in this spe- 

 cies is 32. In 126 cases 

 of diakinesis examined, 

 no association other than 

 bivalent was observed 

 (Figs. 2 a, b). At meta- 

 phase of the first divi- 

 sion pairs of bivalents are 

 seen lying in juxtaposition 

 (Figs. 2 e, f). The degree 

 of association is not so 

 marked as in D. Merckii, 

 and unlike this species 

 some plates may be found 

 in which there is little 

 evidence of secondary as- 

 sociation. A complete side 

 view of first metaphase is 



