546 A. C. WALTON 



I • 



2 t 



3 Ci V Fig. A Chromosome cycle in Ascaris 



, canis. 1, monad chromosome of last 



a, b . 



oogonial stage; 2, dyad chromosome of 



early prophase, first oocyte, showing 

 Querkerbe; 3, tetrad chromosome of 

 later prophase, showing Querkerbe and 

 first longitudinal constriction; a, face 

 view; h, side view; c, end view; 4> two 

 tetrads, late prophase first oocyte, un- 

 dergoing parasyndesis ; 5, di-tetrad 

 formed by the parasyndesis of two te- 

 trads; a, side view; h, end view; 6, first 

 maturation division, along plane of first 

 longitudinal constriction; a, two daugh- 

 ter tetrads separating; b, daughter te- 

 trad, face view; 7, daughter tetrad, sec- 

 ond oocyte; a, face view; b, end view; 

 c, side view; 8, second maturation divi- 

 sion, along plane of parasyndesis; a, b, 

 two daughter dyads; 9, dyad chromo- 

 some, found in ootid, and in 'stem' cells 

 of embryo; a, side view; b, end view; 10, 

 monad chromosome, found in soma cells 

 of embryo after 'diminution'; 11, monad 

 chromosome, found in propagation cells 

 of embryo (Querkerbe suppressed). 



II t 



