REDUCTION WITHOUT TETRAD-FORMATION 



261 



seen during the foregoing anaphases. There is therefore no evi- 

 dence of a transverse division. McGregor ('99) describes a nearly 

 sniiilar process in Amphiuma, where the longitudinal division of the 



A 



X 



\ 



!0 



c 



4"<** + 



r 



D 



' I > 





-/^■^ 



\ 



■'f^?^-^ 







^Mil^ 





i».- 



y i> ■■ nf 



! Z' 



J 



V>v^ 



J»s^n«* 



J 



■^ 



G 



// 



y 



y 



Fig. 130. — Maturation in the lamellibranch Zirp/uca and in I/taiasst'/nii. [GRIFFIN.] 



A-E, Zirp/icea; F-/, Thalassema. 



A. Unfertilized ^gg, ring-shaped and cross-shaped chromosomes. D. Prophase of first polar 

 mitosis. C. First polar spindle ; double crosses. D. Slightly later stage. E. The double crosses 

 have broken apart (equation-division). G. Ensuing stage; daughter-V's broken apart at ihe 

 apex. H. Telophase of first, early prophase of second, division ; limbs of tlie V's separate but 

 closely opposed. F. Later prophase of second division. /. Second polar spindle in mctaphase. 



daughter-V's is seen with the greatest clearness throughout the 

 anaphases. 



The weak point in both the foregoing cases is the fact that all 

 traces of the second longitudinal division are lost during the ensuing 



