198 THE AMERICAN NATURALIST [Vol. L1V 



they would give rise to a second ring continuous with the 

 first but at right angles to it, as shown in perspective by 

 Fig. 3 D; and by repetition of this process would be 

 formed a series of three or more interlocking rings, each 

 at right angles to its successor (Fig. 3 E, F). 1 How 

 many such successive rings may be formed is not known. 

 Double rings seem to be the most frequent ; but in Chor- 

 thippus {Stenobothorus) both Eobertson and Wenrich 

 describe and figure triple rings including at least one 

 case in which the lateral arms are long enough to form a 

 fourth ring, though their ends are in fact free. Jans- 

 sens 's diagram (Fig. 1) represents four complete rings 

 with lateral arms at both ends of the series; and it is 

 quite possible, as McClung has suggested, that some of 

 the forms that have been described as twisted or strep- 

 sinema stages may really be early conditions of such 

 multiple rings. 



Janssens has found that in the heterotypic division 

 the double or multiple ring-tetrads lie on the spindle 

 with their longer axis transverse to that of the spindle, 

 and establish a lateral (atelomitic or non-terminal) at- 

 tachment ; and since successive rings are always at right 

 angles to one another they lie alternately either in the 

 equatorial plane of the spindle or in a plane at right 

 angles to it, i. e., tangential to the spindle. In the ensu- 

 ing division the series is cut straight through in the equa- 

 torial plane (as shown in Fig. 1), rings which lie in this 

 plane being split lengthwise while those lying tangen- 

 tially are cut crosswise. This curious result is perfectly 

 in agreement with Eobertson 's observations on Chor- 

 thippus ('16, Figs. 179-182) and those of Wenrich on 

 Trimerotropis ('17, Plate 3, Figs. 17, 18), and we may 

 probably accept it without hesitation, at least for some 

 tetrads of this type. 



Thus far all observers are in agreement concerning the 

 external structure and mode of division of the compound 



i This account does not correctly describe the mode in which these com- 

 pound rings actually arise, but it is a convenient way of making clear their 



