484 JOHN BELLING. 



has arms which taper to the center, the two homologues having 

 apparently joined at the constrictions. The last two drawings 

 in the lowest line of Fig. 3 are the same bivalent at two different 

 focusses, apparently showing one transverse and one reflexed 



FIG. 3. Camera drawings of eight bivalents. ' The four crosses have the nodes 

 at different points, but always at equal distances from the ends of the homologues. 

 The lowest arm of the second cross in the second line is much foreshortened. The 

 last two figures show the effects of change of focus on the node. 



chromatid of one homologue, the same thing being often ob- 

 servable at a different focus in the other homologue also. These 

 are pulled out by the spindle fibers which are attached at the 

 apex of the bend at the median constriction. 



One hundred and sixteen of the long bivalents were classified 

 in six groups (Diagram i), mostly after squeezing chromosomes 

 and cytoplasm from the cell. The results were (Diagram i): 

 38 cases of the ring and V; 20 X's; and 4 figures of 8 (totalling 

 62 with one node) ; 37 cases of the double ring and V; 10 cases 

 of the ring and two V's; and 7 cases of a triple ring; totalling 

 54 cases with two nodes. No bivalents with triple nodes were 

 certainly demonstrated. If only two chromatids underwent 

 segmental interchange at any one node, as seems to be indicated 



