INTRODUCTION TO CYTOLOGY 



conjugation (E) and take the form of rod tetrads (F 2 ) like those described 

 by Riickert and Haecker. While opening out in this manner the longi- 



FIG. 96. Diagram showing the origin of the tetrad of chromatids (D) according to 

 Scheme A (A\-C\) and Scheme B (Az-C*), and the further transformation of this tetrad into 

 tetrads of five types (Fi-F$). 



tudinal halves of each chromosome may diverge where the two chromo- 

 somes remain in contact ("3), the tetrad eventually taking the form of a 

 cross (F 3 ) as in the cases described by Paulmier and by Foot and StrobelL 



